Surface-reacted calcium carbonate with functional cations

ABSTRACT

A process of producing a surface-reacted calcium carbonate is described. In embodiments, a calcium carbonate-comprising material is treated with at least one H3O+ ion donor, carbon dioxide, and at least one water-soluble metal cation source in an aqueous medium to form an aqueous suspension of surface-reacted calcium carbonate. A surface-reacted calcium carbonate obtained by said process and its use are also described.

The present invention relates to a surface-reacted calcium carbonate, aprocess for manufacturing the same, and its use.

In the year of 1998, a new type of surface-reacted calcium carbonate wasfirst described in FR 2787802 B1, subsequently in WO 00/39222 A1 and US2004/0020410 A1, and is based on the reaction of natural ground calciumcarbonate with gaseous CO₂ and with one or more medium-strong to strongH₃O^(|) ion providers. The obtained product is a porous calciumcarbonate having a special surface structure, porosity, and specificsurface area providing a reduction in the weight of paper for a constantsurface area without loss of physical properties, when it is used as apigment or coating filler for the said paper.

In WO 2004/083316 A1, a further advantageous modification in thepreparation of this surface-reacted calcium carbonate is described,wherein aluminium silicate, synthetic silica, calcium silicate,silicates and/or monovalent salt are involved, and which are also usefulin paper-making applications.

Also, WO 2005/121257 A2 refers to the addition of advantageous additivesin the production of said surface-reacted calcium carbonate, wherein oneor more compounds of formula R-X are added, which, e.g. are selectedfrom fatty acids, fatty amines or fatty alcohols.

WO 2009/074492 A1 especially relates to the optimization of the knownprocess as regards precipitated calcium carbonate, as it turned out thatdue to the special conditions in the precipitation of calcium carbonate,the process useful for natural ground calcium carbonate did not providethe same good results for the surface-reaction of synthetic precipitatedcalcium carbonate.

Several further optimizations and modifications of the process for thepreparation of surface-reacted calcium carbonate followed such as thosedescribed in

WO 2010/146530 A1 and WO 2010/146531 A1 involving the use of weak acidsin the preparation of surface-reacted calcium carbonate.

EP 2 957 603 A1 describes a method for producing granules comprisingsurface-reacted calcium carbonate.

The characteristics of these particulate materials may be furtherimproved or modified by additional surface-treatments, for example, inorder to improve hydrophobicity/hydrophilicity or acid-resistance.Another aim is to locate surface-treatment agents on the surface ofthese particulate materials in order to use them as carrier material.

For example, EP 1 084 203 refers to composite compositions comprising atleast two mineral or organic fillers or pigments and at least onebinding agent. The mineral or organic fillers or pigments have undergonea physical or chemical treatment such that they have at least oneorganophilic site.

EP 2 029 675 refers to composites of inorganic and/or organicmicroparticles and nano-calcium carbonate particles. The surface ofthese particulate materials is coated with the help of binders.

US 2012/0202684 relates to high surface area materials, such asnanoparticles, which are coated with metal ions by absorbing the metalions on the surface of the nanoparticles. The obtained modifiedparticles can be used for removing gaseous compounds or for neutralizingodour.

However, there is still a need in the art for methods for producingsurface-reacted calcium carbonate, and, in particular, modifiedsurface-reacted calcium carbonate, which provides additionalfunctionalities.

Aqueous preparations, for example, and especially suspensions,dispersions or slurries of minerals, fillers or pigments, which are usedextensively in the paper, paint, rubber and plastics industries ascoatings, fillers, extenders and pigments for papermaking as well asaqueous lacquers and paints are often subject to microbialcontamination. Such a contamination can result in changes in thepreparation properties such as changes in viscosity and/or pH,discolorations or reductions in other quality parameters, whichnegatively affect their commercial value. The contaminated filleraqueous preparations may also transmit the microorganisms to the laterproduced product, for example, the plastic or paper product. Therefore,for ensuring an acceptable microbiological quality of aqueouspreparations, preservatives or biocides are used over the entire lifecycle of the preparation (production, storage, transport, use).

Preservatives are also typically added to pharmaceutical, cosmetic orfood products to prevent decomposition by microbial growth or byundesirable chemical changes and to avoid any health hazards. However,many of these preservatives are themselves subject to health concerns,and thus, are increasingly rejected by consumers.

Dry film preservation, meaning preservation of dry products such ascoatings and building materials from microbiological degradation toavoid material destruction and visible disfigurement, is also animportant and difficult challenge. Preservatives for dry filmpreservation are typically incorporated in the product and preserve thedry product over a longer period of time by an antimicrobial activity onthe dry or wet surface. Such an antimicrobial surface activity is ofadvantage not only to protect the product itself from degradation ordefacement but also to avoid contamination of a surface with pathogenicmicroorganisms. This is particular useful in the health care sector.However, there is the risk that preservatives are eluted from the dryproduct over time, for example, due to rain or humid environment, whichmay pose a danger to human health and the environment.

US 2006/0246149 A1 describes antimicrobial pigments, which areobtainable by agitating a suspension comprising one or more pigments andsilver oxide as antimicrobial compound. A modified mineral-based fillerwith enhanced retention of at least one active ingredient or enhancedantimicrobial capabilities is disclosed in US 2010/0260866. A studyconcerning copper precipitation from sulphate solutions with calciumcarbonate was published by Zhizhaev et al. (Russian Journal of AppliedChemistry 2007, 80(10), 1632-1635).

However, there is still a need in the art for harmless materials withantimicrobial activity, which are suitable for a wide range ofapplications.

Accordingly, it is an object of the present invention to provide aprocess for producing a surface-reacted calcium carbonate which providesfurther functionalities. It is desirable that the obtainedsurface-reacted calcium carbonate can be used as filler material so thatit may replace conventionally used fillers in various applications orsupplement them.

It is also an object of the present invention to provide a material,which is at least partially derivable from natural sources and is notpersistent in the environment, but easily biodegradable. It would alsobe desirable that said material is water-resistant, and thus, can beused in application subjected to regular water washings. It is alsodesirable that the functionality of the surface-reacted calciumcarbonate can be controlled and can be tailored for a specificapplication.

It is also an object of the present invention to provide a materialwhich can control microbial contamination but does not represent ahazard to health. It is a further object of the present invention toprovide a material which, besides the antimicrobial activity, hasadditional benefits. For example, it would be desirable that such amaterial confers or enhances the antimicrobial activity of a product, inwhich it is incorporated, over an extended period without affecting theproperties of the product in a negative way. It would also be desirableto provide a material that is suitable for agricultural applications andcan release micronutrients to plants.

The foregoing and other objects are solved by the subject-matter asdefined in the independent claims.

According to one aspect of the present invention, a process forproducing a surface-reacted calcium carbonate is provided, the processcomprising the steps of:

-   -   a) providing a calcium carbonate-comprising material,    -   b) providing at least one H₃O⁺ ion donor,    -   c) providing at least one water-soluble metal cation source, and    -   d) treating the calcium carbonate-comprising material of step a)        with the at least one H₃O⁺ ion donor of step b) and carbon        dioxide in an aqueous medium to form an aqueous suspension of        surface-reacted calcium carbonate,    -   wherein the carbon dioxide is formed in-situ by the H₃O⁺ ion        donor treatment and/or is supplied from an external source, and    -   wherein the at least one water-soluble metal cation source of        step c) is added during step d).

According to a further aspect, a surface-reacted calcium carbonateobtainable by a process according to the present invention is provided.

According to still a further aspect, a composition comprising asurface-reacted calcium carbonate according to the present invention isprovided, preferably further comprising an additional surface-reactedcalcium carbonate, wherein the additional surface-reacted calciumcarbonate is a reaction product of natural ground calcium carbonate orprecipitated calcium carbonate with carbon dioxide and at least one H₃O⁺ion donor, wherein the carbon dioxide is formed in-situ by the H₃O⁺ iondonor treatment and/or is supplied from an external source.

According to still a further aspect, a use of a surface-reacted calciumcarbonate according to the present invention or a composition accordingto the present invention as preservative, for the control of odour,and/or for enhancing and/or mediating antimicrobial activity of asubstrate is provided.

According to still a further aspect, a use of a surface-reacted calciumcarbonate according to the present invention or a composition accordingto the present invention as a metal cation releaser, preferably asmicronutrient delivery agent and/or plant protection product isprovided.

According to still a further aspect, a use of a surface-reacted calciumcarbonate according to the present invention or a composition accordingto the present invention for enhancing the electrical conductivity of asubstrate is provided.

According to still a further aspect, use of a surface-reacted calciumcarbonate according to the present invention or a composition accordingto the present invention in polymer applications, paper coatingapplications, paper making, paints, coatings, sealants, printing inks,adhesives, food, feed, pharmaceuticals, concrete, cement, cosmetics,water treatment, engineered wood applications, plasterboardapplications, packaging applications and/or agricultural applications isprovided.

According to still a further aspect, an article comprising asurface-reacted calcium carbonate according to the present invention ora composition according to the present invention is provided, whereinthe article is selected from paper products, engineered wood products,plasterboard products, polymer products, hygiene products, medicalproducts, healthcare products, filter products, woven materials,nonwoven materials, geotextile products, agricultural products,horticultural products, clothing, footwear products, baggage products,household products, industrial products, packaging products, buildingproducts, and construction products.

Advantageous embodiments of the present invention are defined in thecorresponding subclaims.

According to one embodiment the calcium carbonate-comprising material isa natural ground calcium carbonate and/or a precipitated calciumcarbonate, preferably the natural ground calcium carbonate is selectedfrom the group consisting of marble, chalk, dolomite, limestone, andmixtures thereof, and/or the precipitated calcium carbonate is selectedfrom the group consisting of precipitated calcium carbonates having anaragonitic, vateritic or calcitic crystal form, and mixtures thereof.According to a further embodiment the calcium carbonate-comprisingmaterial is in form of particles having a weight median particle sized₅₀(wt) from 0.05 to 10 μm, preferably from 0.2 to 5.0 μm, morepreferably from 0.4 to 3.0 μm, and most preferably from 0.6 to 1.2 μm,and/or a weight top cut particle size d₉₈(wt) from 0.15 to 55 μm,preferably from 1 to 40 μm, more preferably from 2 to 25 μm, and mostpreferably from 3 to 15 μm.

According to one embodiment the at least one H₃O⁺ ion donor is selectedfrom the group consisting of hydrochloric acid, sulphuric acid,sulphurous acid, phosphoric acid, citric acid, oxalic acid, an acidicsalt, acetic acid, formic acid, and mixtures thereof, preferably the atleast one H₃O⁺ ion donor is selected from the group consisting ofhydrochloric acid, sulphuric acid, sulphurous acid, phosphoric acid,oxalic acid, H₂PO₄ ⁻, being at least partially neutralised by a cationselected from Li^(|), Na⁺ and/or K⁺, HPO₄ ²⁻, being at least partiallyneutralised by a cation selected from Li⁺, Na⁺, K⁺, Mg²⁺, and/or Ca²⁻,and mixtures thereof, more preferably the at least one H₃O⁺ ion donor isselected from the group consisting of hydrochloric acid, sulphuric acid,sulphurous acid, phosphoric acid, oxalic acid, or mixtures thereof, andmost preferably, the at least one H₃O⁺ ion donor is phosphoric acid.According to a further embodiment the molar ratio of the at least oneH₃O⁺ ion donor to the calcium carbonate-comprising material is from 0.01to 4, preferably from 0.02 to 2, more preferably from 0.05 to 1, andmost preferably from 0.1 to 0.58.

According to one embodiment the at least one water-soluble metal cationsource is selected from the group consisting of a water-soluble metalsalt, a water-soluble transition metal complex, a water-soluble metalhydroxide, a water-soluble metal oxide, and mixtures thereof, preferablythe water-soluble metal cation source is selected from the groupconsisting of a water-soluble transition metal salt, a water-solublegroup(III) metal salt, and mixtures thereof, more preferably thewater-soluble metal cation source is selected from the group consistingof water-soluble salts of aluminium, chromium, manganese, iron, cobalt,nickel, copper, zinc, silver, gold, zirconium, platinum, palladium, andmixtures thereof, and most preferably the water-soluble metal cationsource is selected from the group consisting of copper nitrate, coppersulphate, copper acetate, copper chloride, copper bromide, copperiodide, zinc nitrate, zinc sulphate, zinc acetate, zinc chloride, zincbromide, zinc iodide, hydrates thereof, and mixtures thereof. Accordingto a further embodiment the at least one water-soluble metal cationsource is provided in an amount from 0.01 to 60 wt.-%, based on thetotal weight of the calcium carbonate-comprising material, preferablyfrom 0.05 to 50 wt.-%, more preferably from 0.1 to 25 wt.-%, and mostpreferably from 0.5 to 10 wt.-%.

According to one embodiment in step d) the calcium carbonate-comprisingmaterial is treated with a solution comprising the at least one H₃O⁺ iondonor of step b) and the at least one water-soluble metal cation sourceof step c). According to a further embodiment in step d) the calciumcarbonate-comprising material is treated with a first solutioncomprising a first part of the at least one H₃O⁺ ion donor of step b),and subsequently, with a second solution comprising the remaining partof the at least one H₃O⁺ ion donor of step b) and the at least onewater-soluble metal cation source of step c). According to still afurther embodiment step d) is carried out at a temperature from 20 to90° C., preferably from 30 to 85° C., more preferably from 40 to 80° C.,even more preferably from 50 to 75° C., and most preferably from 60 to70° C.

According to one embodiment the process further comprises a step e) ofseparating the surface-reacted calcium carbonate from the aqueoussuspension obtained in step d). According to a further embodiment theprocess further comprises a step f) of drying the surface-reactedcalcium carbonate after step d) or after step e), if present, at atemperature in the range from 60 to 600° C., preferably until themoisture content of the surface-reacted calcium carbonate is between0.01 and 5 wt.-%, based on the total weight of the dried surface-reactedcalcium carbonate.

According to one embodiment the calcium carbonate-comprising material isa natural ground calcium carbonate, the at least one H₃O⁺ ion donor isphosphoric acid, the at least one water-soluble metal cation source isselected from the group consisting of copper nitrate, copper sulphate,copper acetate, copper chloride, copper bromide, copper iodide, zincnitrate, zinc sulphate, zinc acetate, zinc chloride, zinc bromide, zinciodide, hydrates thereof, and mixtures thereof, and in step d) thecalcium carbonate-comprising material is treated with a solutioncomprising the at least one H₃O⁺ ion donor of step b) and the at leastone water-soluble metal cation source of step c).

According to one embodiment the surface-reacted calcium carbonate has aspecific surface area of from 15 m²/g to 200 m²/g, preferably from 20m²/g to 180 m²/g, more preferably from 25 m²/g to 160 m²/g, even morepreferably from 27 m²/g to 150 m²/g, most preferably from 30 m²/g to 140m²/g, measured using nitrogen and the BET method. According to a furtherembodiment the surface-reacted calcium carbonate has a volume determinedmedian particle size d₅₀(vol) from 1 to 75 μm, preferably from 2 to 50μm, more preferably from 3 to 40 μm, even more preferably from 4 to 30μm, and most preferably from 5 to 15 μm, and/or a volume determined topcut particle size d₉₈(vol) from 2 to 150 μm, preferably from 4 to 100μm, more preferably from 6 to 80 μm, even more preferably from 8 to 60μm, and most preferably from 10 to 30 μm.

According to one embodiment the surface-reacted calcium carbonate has anintra-particle intruded specific pore volume in the range from 0.1 to2.3 cm³/g, preferably from 0.2 to 2.0 cm³/g, more preferably from 0.4 to1.8 cm³/g, and most preferably from 0.6 to 1.6 cm³/g, calculated frommercury porosimetry measurement. According to a further embodiment thesurface-reacted calcium carbonate has an intra-particle pore size in arange of from 0.004 to 1.6 μm, preferably in a range of between 0.005 to1.3 μm, more preferably from 0.006 to 1.15 μm, and most preferably of0.007 to 1.0 μm, determined from mercury porosity measurement.

It should be understood that for the purpose of the present invention,the following terms have the following meaning:

A “calcium carbonate-comprising material” in the meaning of the presentinvention can be a mineral material or a synthetic material having acontent of calcium carbonate of at least 50 wt.-%, preferably 75 wt.-%,more preferably 90 wt.-%, and most preferably 95 wt.-%, based on thetotal weight of the calcium carbonate-comprising material.

For the purpose of the present application, “water-insoluble” materialsare defined as materials which, when 100 g of said material is mixedwith 100 g deionised water and filtered on a filter having a 0.2 μm poresize at 20° C. to recover the liquid filtrate, provide less than orequal to 1 g of recovered solid material following evaporation at 95 to100° C. of 100 g of said liquid filtrate at ambient pressure.“Water-soluble” materials are defined as materials which, when 100 g ofsaid material is mixed with 100 g deionised water and filtered on afilter having a 0.2 μm pore size at 20° C. to recover the liquidfiltrate, provide more than 1 g of recovered solid material followingevaporation at 95 to 100° C. of 100 g of said liquid filtrate at ambientpressure.

“Natural ground calcium carbonate” (GCC) in the meaning of the presentinvention is a calcium carbonate obtained from natural sources, such aslimestone, marble, or chalk, and processed through a wet and/or drytreatment such as grinding, screening and/or fractionating, for example,by a cyclone or classifier.

“Precipitated calcium carbonate” (PCC) in the meaning of the presentinvention is a synthesised material, obtained by precipitation followingreaction of carbon dioxide and lime in an aqueous, semi-dry or humidenvironment or by precipitation of a calcium and carbonate ion source inwater. PCC may be in the vateritic, calcitic or aragonitic crystal form.PCCs are described, for example, in EP 2 447 213 A1, EP 2 524 898 A1, EP2 371 766 A1, EP 1 712 597 A1, EP 1 712 523 A1, or WO 2013/142473 A1.

The term “surface-reacted” in the meaning of the present applicationshall be used to indicate that a material has been subjected to aprocess comprising partial dissolution of said material upon acidictreatment (e.g., by use of water-soluble free acids and/or acidic salts)in aqueous environment followed by a crystallization process which mayoccur in the absence or presence of further crystallization additives.The term “acid” as used herein refers to an acid in the meaning of thedefinition by Brønsted and Lowry (e.g., H₂SO₄, HSO₄ ⁻), wherein the term“free acid” refers only to those acids being in the fully protonatedform (e.g., H₂SO₄).

The “particle size” of particulate materials other than surface-reactedcalcium carbonate herein is described by its distribution of particlesizes d_(x). Therein, the value d_(x) represents the diameter relativeto which x % by weight of the particles have diameters less than d_(x).This means that, for example, the d₂₀ value is the particle size atwhich 20 wt.-% of all particles are smaller than that particle size. Thed₅₀ value is thus the weight median particle size, i.e. 50 wt.-% of allparticles are smaller than this particle size. For the purpose of thepresent invention, the particle size is specified as weight medianparticle size d₅₀(wt.) unless indicated otherwise. Particle sizes weredetermined by using a Sedigraph™ 5100 instrument or Sedigraph™ 5120instrument of Micromeritics Instrument Corporation. The method and theinstrument are known to the skilled person and are commonly used todetermine the particle size of fillers and pigments. The measurementswere carried out in an aqueous solution of 0.1 wt.-% Na₄P₂O₇.

The “particle size” of surface-reacted calcium carbonate herein isdescribed as volume-based particle size distribution. Volume-basedmedian particle size d₅₀ was evaluated using a Malvern Mastersizer 2000Laser Diffraction System. The d₅₀ or d₉₈ value, measured using a MalvernMastersizer 2000 Laser Diffraction System, indicates a diameter valuesuch that 50% or 98% by volume, respectively, of the particles have adiameter of less than this value. The raw data obtained by themeasurement are analysed using the Mie theory, with a particlerefractive index of 1.57 and an absorption index of 0.005.

The “specific surface area” (expressed in m²/g) of a material as usedthroughout the present document can be determined by the Brunauer EmmettTeller (BET) method with nitrogen as adsorbing gas and by use of a ASAP2460 instrument from Micromeritics. The method is well known to theskilled person and defined in ISO 9277:2010. Samples are conditioned at100° C. under vacuum for a period of 30 min prior to measurement. Thetotal surface area (in m²) of said material can be obtained bymultiplication of the specific surface area (in m²/g) and the mass (ing) of the material.

In the context of the present invention, the term “pore” is to beunderstood as describing the space that is found between and/or withinparticles, i.e. that is formed by the particles as they pack togetherunder nearest neighbour contact (interparticle pores), such as in apowder or a compact and/or the void space within porous particles(intraparticle pores), and that allows the passage of liquids underpressure when saturated by the liquid and/or supports absorption ofsurface wetting liquids.

The specific pore volume is measured using a mercury intrusionporosimetry measurement using a Micromeritics Autopore V 9620 mercuryporosimeter having a maximum applied pressure of mercury 414 MPa (60 000psi), equivalent to a Laplace throat diameter of 0.004 μm (˜nm). Theequilibration time used at each pressure step is 20 seconds. The samplematerial is sealed in a 3 cm³ chamber powder penetrometer for analysis.The data are corrected for mercury compression, penetrometer expansionand sample material compression using the software Pore-Comp (Gane, P.A. C., Kettle, J. P., Matthews, G. P. and Ridgway, C. J., “Void SpaceStructure of Compressible Polymer Spheres and Consolidated CalciumCarbonate Paper-Coating Formulations”, Industrial and EngineeringChemistry Research, 35(5), 1996, p1753-1764.).

The total pore volume seen in the cumulative intrusion data can beseparated into two regions with the intrusion data from 214 μm down toabout 1-4 μm showing the coarse packing of the sample between anyagglomerate structures contributing strongly. Below these diameters liesthe fine interparticle packing of the particles themselves. If they alsohave intraparticle pores, then this region appears bi modal, and bytaking the specific pore volume intruded by mercury into pores finerthan the modal turning point, i.e. finer than the bi-modal point ofinflection, we thus define the specific intraparticle pore volume. Thesum of these three regions gives the total overall pore volume of thepowder, but depends strongly on the original sample compaction/settlingof the powder at the coarse pore end of the distribution.

By taking the first derivative of the cumulative intrusion curve thepore size distributions based on equivalent Laplace diameter, inevitablyincluding pore-shielding, are revealed. The differential curves clearlyshow the coarse agglomerate pore structure region, the interparticlepore region and the intraparticle pore region, if present. Knowing theintraparticle pore diameter range it is possible to subtract theremainder interparticle and interagglomerate pore volume from the totalpore volume to deliver the desired pore volume of the internal poresalone in terms of the pore volume per unit mass (specific pore volume).The same principle of subtraction, of course, applies for isolating anyof the other pore size regions of interest.

For the purpose of the present invention, the “solids content” of aliquid composition is a measure of the amount of material remainingafter all the solvent or water has been evaporated. If necessary, the“solids content” of a suspension given in wt.-% in the meaning of thepresent invention can be determined using a Moisture Analyzer HR73 fromMettler-Toledo (T=120° C., automatic switch off 3, standard drying) witha sample size of 5 to 20 g.

Unless specified otherwise, the term “drying” refers to a processaccording to which at least a portion of water is removed from amaterial to be dried such that a constant weight of the obtained “dried”material at 120° C. is reached. Moreover, a “dried” or “dry” materialmay be defined by its total moisture content which, unless specifiedotherwise, is less than or equal to 1.0 wt.-%, preferably less than orequal to 0.5 wt.-%, more preferably less than or equal to 0.2 wt.-%, andmost preferably between 0.03 and 0.07 wt.-%, based on the total weightof the dried material.

For the purpose of the present invention, the term “viscosity” or“Brookfield viscosity” refers to Brookfield viscosity. The Brookfieldviscosity is for this purpose measured by a Brookfield DV-II+ Proviscometer at 25° C.±1° C. at 100 rpm using an appropriate spindle ofthe Brookfield RV-spindle set and is specified in mPa·s. Based on histechnical knowledge, the skilled person will select a spindle from theBrookfield RV-spindle set which is suitable for the viscosity range tobe measured. For example, for a viscosity range between 200 and 800mPa·s the spindle number 3 may be used, for a viscosity range between400 and 1 600 mPa·s the spindle number 4 may be used, for a viscosityrange between 800 and 3 200 mPa·s the spindle number 5 may be used, fora viscosity range between 1 000 and 2 000 000 mPa·s the spindle number 6may be used, and for a viscosity range between 4 000 and 8 000 000 mPa·sthe spindle number 7 may be used.

A “suspension” or “slurry” in the meaning of the present inventioncomprises undissolved solids and water, and optionally furtheradditives, and usually contains large amounts of solids and, thus, ismore viscous and can be of higher density than the liquid from which itis formed.

Where an indefinite or definite article is used when referring to asingular noun, e.g., “a”, “an” or “the”, this includes a plural of thatnoun unless anything else is specifically stated.

Where the term “comprising” is used in the present description andclaims, it does not exclude other elements. For the purposes of thepresent invention, the term “consisting of” is considered to be apreferred embodiment of the term “comprising”. If hereinafter a group isdefined to comprise at least a certain number of embodiments, this isalso to be understood to disclose a group, which preferably consistsonly of these embodiments.

Terms like “obtainable” or “definable” and “obtained” or “defined” areused interchangeably. This, for example, means that, unless the contextclearly dictates otherwise, the term “obtained” does not mean toindicate that, for example, an embodiment must be obtained by, forexample, the sequence of steps following the term “obtained” though sucha limited understanding is always included by the terms “obtained” or“defined” as a preferred embodiment.

Whenever the terms “including” or “having” are used, these terms aremeant to be equivalent to “comprising” as defined hereinabove.

The inventive process for producing a surface-reacted calcium carbonatecomprises the steps of a) providing a calcium carbonate-comprisingmaterial, b) providing at least one H₃O⁺ ion donor, c) providing atleast one water-soluble metal cation source, and d) treating the calciumcarbonate-comprising material of step a) with the at least one H₃O⁺ iondonor of step b) and carbon dioxide in an aqueous medium to form anaqueous suspension of surface-reacted calcium carbonate. The carbondioxide is formed in-situ by the H₃O⁺ ion donor treatment and/or issupplied from an external source. The at least one water-soluble metalcation source of step c) is added during step d).

In the following preferred embodiments of the inventive composition willbe set out in more detail. It is to be understood that these embodimentsand details also apply to the inventive products and uses.

Process Step a)

According to step a) of the process of the present invention, acalcium-carbonate comprising material is provided.

According to one embodiment the at least one calciumcarbonate-comprising material has a content of calcium carbonate of atleast 50 wt.-%, preferably 75 wt.-%, more preferably 90 wt.-%, and mostpreferably 95 wt.-%, based on the total weight of the calciumcarbonate-comprising material. According to another embodiment the atleast one calcium carbonate comprising material consists of calciumcarbonate.

The calcium carbonate-comprising material may be selected from naturalground calcium carbonate, precipitated calcium carbonate, dolomite, ormixtures thereof. The natural ground calcium carbonate may be preferablyselected from marble, limestone and/or chalk, and/or the precipitatedcalcium carbonate may be preferably selected from vaterite, calciteand/or aragonite

According to one embodiment of the present invention, the calciumcarbonate-comprising material is a natural ground calcium carbonateand/or a precipitated calcium carbonate, preferably the natural groundcalcium carbonate is selected from the group consisting of marble,chalk, dolomite, limestone, and mixtures thereof, and/or theprecipitated calcium carbonate is selected from the group consisting ofprecipitated calcium carbonates having an aragonitic, vateritic orcalcitic crystal form, and mixtures thereof.

“Natural ground calcium carbonate” (GCC) is understood to bemanufactured from a naturally occurring form of calcium carbonate, minedfrom sedimentary rocks such as limestone or chalk, or from metamorphicmarble rocks, eggshells or seashells. Calcium carbonate is known toexist as three types of crystal polymorphs: calcite, aragonite andvaterite. Calcite, the most common crystal polymorph, is considered tobe the most stable crystal form of calcium carbonate. Less common isaragonite, which has a discrete or clustered needle orthorhombic crystalstructure. Vaterite is the rarest calcium carbonate polymorph and isgenerally unstable. Ground calcium carbonate is almost exclusively ofthe calcitic polymorph, which is said to be trigonal-rhombohedral andrepresents the most stable form of the calcium carbonate polymorphs. Theterm “source” of the calcium carbonate in the meaning of the presentapplication refers to the naturally occurring mineral material fromwhich the calcium carbonate is obtained. The source of the calciumcarbonate may comprise further naturally occurring components such asmagnesium carbonate, alumino silicate etc.

In general, the grinding of natural ground calcium carbonate may be adry or wet grinding step and may be carried out with any conventionalgrinding device, for example, under conditions such that comminutionpredominantly results from impacts with a secondary body, i.e. in one ormore of: a ball mill, a rod mill, a vibrating mill, a roll crusher, acentrifugal impact mill, a vertical bead mill, an attrition mill, a pinmill, a hammer mill, a pulveriser, a shredder, a de-clumper, a knifecutter, or other such equipment known to the skilled man. In case thecalcium carbonate containing mineral material comprises a wet groundcalcium carbonate containing mineral material, the grinding step may beperformed under conditions such that autogenous grinding takes placeand/or by horizontal ball milling, and/or other such processes known tothe skilled man. The wet processed ground calcium carbonate containingmineral material thus obtained may be washed and dewatered by well-knownprocesses, e.g. by flocculation, filtration or forced evaporation priorto drying. The subsequent step of drying (if necessary) may be carriedout in a single step such as spray drying, or in at least two steps. Itis also common that such a mineral material undergoes a beneficiationstep (such as a flotation, bleaching or magnetic separation step) toremove impurities.

According to one embodiment of the present invention the source ofnatural ground calcium carbonate (GCC) is selected from marble, chalk,limestone, or mixtures thereof. Preferably, the source of ground calciumcarbonate is marble, and more preferably dolomitic marble and/ormagnesitic marble. According to one embodiment of the present inventionthe GCC is obtained by dry grinding. According to another embodiment ofthe present invention the GCC is obtained by wet grinding and subsequentdrying.

According to one embodiment of the present invention, the calciumcarbonate comprises one type of natural ground calcium carbonate.According to another embodiment of the present invention, the calciumcarbonate comprises a mixture of two or more types of natural groundcalcium carbonates selected from different sources.

“Precipitated calcium carbonate” (PCC) in the meaning of the presentinvention is a synthesized material, generally obtained by precipitationfollowing reaction of carbon dioxide and calcium hydroxide in an aqueousenvironment or by precipitation of calcium and carbonate ions, forexample CaCl₂ and Na₂CO₃, out of solution. Further possible ways ofproducing PCC are the lime soda process, or the Solvay process in whichPCC is a by-product of ammonia production. Precipitated calciumcarbonate exists in three primary crystalline forms: calcite, aragoniteand vaterite, and there are many different polymorphs (crystal habits)for each of these crystalline forms. Calcite has a trigonal structurewith typical crystal habits such as scalenohedral (S-PCC), rhombohedral(R-PCC), hexagonal prismatic, pinacoidal, colloidal (C-PCC), cubic, andprismatic (P-PCC). Aragonite is an orthorhombic structure with typicalcrystal habits of twinned hexagonal prismatic crystals, as well as adiverse assortment of thin elongated prismatic, curved bladed, steeppyramidal, chisel shaped crystals, branching tree, and coral orworm-like form. Vaterite belongs to the hexagonal crystal system. Theobtained PCC slurry can be mechanically dewatered and dried.

According to one embodiment of the present invention, the precipitatedcalcium carbonate is precipitated calcium carbonate, preferablycomprising aragonitic, vateritic or calcitic mineralogical crystal formsor mixtures thereof.

Precipitated calcium carbonate may be ground prior to the treatment withcarbon dioxide and at least one H₃O⁺ ion donor by the same means as usedfor grinding natural ground calcium carbonate as described above.

“Dolomite” in the meaning of the present invention is a calciumcarbonate containing mineral, namely a carboniccalcium-magnesium-mineral, having the chemical composition of CaMg(CO₃)₂(“CaCO₃.MgCO₃”). A dolomite mineral may contain at least 30.0 wt.-%MgCO₃, based on the total weight of dolomite, preferably more than 35.0wt.-%, and more preferably more than 40.0 wt.-% MgCO₃.

According to one embodiment of the present invention, the calciumcarbonate-comprising material is in form of particles having a weightmedian particle size d₅₀ of 0.05 to 10.0 μm, preferably 0.2 to 5.0 μm,more preferably 0.4 to 3.0 μm, and most preferably 0.6 to 1.2 μm.

According to a further embodiment of the present invention, the calciumcarbonate-comprising material is in form of particles having a top cutparticle size d₉₈ of 0.15 to 55 μm, preferably 1 to 40 μm, morepreferably 2 to 25 μm, and most preferably 3 to 15 μm.

The calcium carbonate-comprising material may have a specific surfacearea (BET) from 1 to 200 m²/g, as measured using nitrogen and the BETmethod according to ISO 9277. According to one embodiment the specificsurface area (BET) of the calcium carbonate-comprising material is from1 to 150 m²/g, preferably from 2 to 60 m²/g, and more preferably from 2to 15 m²/g, as measured using nitrogen and the BET method according toISO 9277.

The calcium carbonate-comprising material may be used dry or in form ofan aqueous suspension. According to a preferred embodiment, the calciumcarbonate-comprising material is in form of an aqueous suspension havinga solids content within the range of 1 wt.-% to 90 wt.-%, preferably 3wt.-% to 60 wt.-%, more preferably 5 wt.-% to 40 wt.-%, and mostpreferably 10 wt.-% to 25 wt.-%, based on the weight of the aqueoussuspension.

The term “aqueous” suspension refers to a system, wherein the liquidphase comprises, preferably consists of, water. However, said term doesnot exclude that the liquid phase of the aqueous suspension comprisesminor amounts of at least one water-miscible organic solvent selectedfrom the group comprising methanol, ethanol, acetone, acetonitrile,tetrahydrofuran and mixtures thereof. If the aqueous suspensioncomprises at least one water-miscible organic solvent, the liquid phaseof the aqueous suspension comprises the at least one water-miscibleorganic solvent in an amount of from 0.1 to 40.0 wt.-% preferably from0.1 to 30.0 wt.-%, more preferably from 0.1 to 20.0 wt.-% and mostpreferably from 0.1 to 10.0 wt.-%, based on the total weight of theliquid phase of the aqueous suspension. For example, the liquid phase ofthe aqueous suspension consists of water.

According to a preferred embodiment of the present invention, theaqueous suspension consists of water and the calciumcarbonate-comprising material.

Alternatively, the aqueous suspension of the calciumcarbonate-comprising material may comprise further additives, forexample, a dispersant. A suitable dispersant may be selected frompolyphosphates, and is in particular a tripolyphosphate. Anothersuitable dispersant may be selected from the group comprisinghomopolymers or copolymers of polycarboxylic acid salts based on, forexample, acrylic acid, methacrylic acid, maleic acid, fumaric acid oritaconic acid and acrylamide or mixtures thereof. Homopolymers orcopolymers of acrylic acid are especially preferred. The weight averagemolecular weight M_(w) of such products is preferably in the range from2 000 to 15 000 g/mol, with a weight average molecular weight M_(w) from3 000 to 7 000 g/mol or 3 500 to 6 000 g/mol being especially preferred.According to an exemplary embodiment, the dispersant is sodiumpolyacrylate having a weight average molecular weight M_(w) from 2 000to 15 000 g/mol, preferably from 3 000 to 7 000 g/mol, and mostpreferably from 3 500 to 6 000 g/mol.

According to one embodiment of the present invention, the calciumcarbonate-comprising material provided in process step a) is naturalground calcium carbonate and/or precipitated calcium carbonate,preferably an aqueous suspension of natural ground calcium carbonateand/or precipitated calcium carbonate having a solids content within therange of 1 wt.-% to 90 wt.-%, preferably 3 wt.-% to 60 wt.-%, morepreferably 5 wt.-% to 40 wt.-%, and most preferably 10 wt.-% to 25wt.-%, based on the weight of the aqueous suspension

Process Step b)

According to step b) of the process of the present invention, at leastone H₃O⁺ ion donor is provided. An “H₃O^(|) ion donor” in the context ofthe present invention is a Brønsted acid and/or an acid salt, i.e. asalt containing an acidic hydrogen.

The at least one H₃O⁺ ion donor may be any strong acid, medium-strongacid, or weak acid, or a mixture thereof, generating H₃O⁺ ions under thepreparation conditions. According to the present invention, the at leastone H₃O⁺ ion donor can also be an acid salt, generating H₃O⁺ ions underthe preparation conditions.

According to one embodiment, the at least one H₃O⁺ ion donor is a strongacid having a pK_(a) of 0 or less at 20° C. According to anotherembodiment, the at least one H₃O⁺ ion donor is a medium-strong acidhaving a pK_(a) value from 0 to 2.5 at 20° C.

If the pK_(a) at 20° C. is 0 or less, the acid is preferably selectedfrom sulphuric acid, hydrochloric acid, or mixtures thereof. If thepK_(a) at 20° C. is from 0 to 2.5, the H₃O⁺ ion donor is preferablyselected from H₂SO₃, H₃PO₄, oxalic acid, or mixtures thereof. The atleast one H₃O⁺ ion donor can also be an acid salt, for example, HSO₄ ⁻or H₂PO₄ ⁻, being at least partially neutralized by a correspondingcation such as Li⁻, Na⁺ or K⁺, or HPO₄ ²⁻, being at least partiallyneutralised by a corresponding cation such as Li⁺, Na^(−, K) ⁺, Mg²⁺ orCa²⁺. The at least one H₃O⁺ ion donor can also be a mixture of one ormore acids and one or more acid salts.

According to still another embodiment, the at least one H₃O⁺ ion donoris a weak acid having a pK_(a) value of greater than 2.5 and less thanor equal to 7, when measured at 20° C., associated with the ionisationof the first available hydrogen, and having a corresponding anion, whichis capable of forming water-soluble calcium salts. Subsequently, atleast one water-soluble salt, which in the case of a hydrogen-containingsalt has a pK_(a) of greater than 7, when measured at 20° C., associatedwith the ionisation of the first available hydrogen, and the salt anionof which is capable of forming water-insoluble calcium salts, isadditionally provided. According to the preferred embodiment, the weakacid has a pK_(a) value from greater than 2.5 to 5 at 20° C., and morepreferably the weak acid is selected from the group consisting of aceticacid, formic acid, propanoic acid, and mixtures thereof. Exemplarycations of said water-soluble salt are selected from the groupconsisting of potassium, sodium, lithium and mixtures thereof. In a morepreferred embodiment, said cation is sodium or potassium. Exemplaryanions of said water-soluble salt are selected from the group consistingof phosphate, dihydrogen phosphate, monohydrogen phosphate, oxalate,silicate, mixtures thereof and hydrates thereof. In a more preferredembodiment, said anion is selected from the group consisting ofphosphate, dihydrogen phosphate, monohydrogen phosphate, mixturesthereof and hydrates thereof. In a most preferred embodiment, said anionis selected from the group consisting of dihydrogen phosphate,monohydrogen phosphate, mixtures thereof and hydrates thereof.Water-soluble salt addition may be performed dropwise or in one step. Inthe case of drop wise addition, this addition preferably takes placewithin a time period of 10 minutes. It is more preferred to add saidsalt in one step.

According to one embodiment of the present invention, the at least oneH₃O⁺ ion donor is selected from the group consisting of hydrochloricacid, sulphuric acid, sulphurous acid, phosphoric acid, citric acid,oxalic acid, an acidic salt, acetic acid, formic acid, and mixturesthereof. Preferably the at least one H₃O⁺ ion donor is selected from thegroup consisting of hydrochloric acid, sulphuric acid, sulphurous acid,phosphoric acid, oxalic acid, H₂PO₄ ⁻, being at least partiallyneutralised by a cation selected from Li⁺, Na⁻ and/or K⁺, HPO₄ ²⁻, beingat least partially neutralised by a cation selected from Li⁺, Na^(|),K^(|), Mg^(2|), and/or Ca^(2|), and mixtures thereof, more preferablythe at least one H₃O⁺ ion donor is selected from the group consisting ofhydrochloric acid, sulphuric acid, sulphurous acid, phosphoric acid,oxalic acid, or mixtures thereof, and most preferably, the at least oneH₃O^(|) ion donor is phosphoric acid.

The at least one H₃O⁺ ion donor can be provided in solid form or in formof a solution. According to a preferred embodiment, the at least oneH₃O⁺ ion donor is provided in form of a solution.

According to one embodiment the at least one H₃O⁺ ion donor is providedin form of an aqueous solution comprising the at least one H₃O⁺ iondonor in an amount from 0.1 to 100 wt.-%, based on the total weight ofthe aqueous solution, preferably in an amount from 1 to 80 wt.-%, morepreferably in an amount from 10 to 50 wt.-%, and most preferably in anamount from 20 to 40 wt.-%.

According to one embodiment, the molar ratio of the at least one H₃O⁺ion donor to the calcium carbonate-comprising material is from 0.01 to4, preferably from 0.02 to 2, more preferably from 0.05 to 1, and mostpreferably from 0.1 to 0.58.

According to another embodiment, the at least one H₃O⁺ ion donor isprovided in an amount from 1 to 40 wt.-%, based on the total weight ofthe calcium carbonate-comprising material, preferably from 5 to 30wt.-%, more preferably from 10 to 20 wt.-%, and most preferably from 15to 18 wt.-%.

Process Step c)

According to step c) of the process of the present invention at leastone water-soluble metal cation source is provided.

According to one embodiment the at least one water-soluble metal cationsource is selected from the group consisting of a water-soluble metalsalt, a water-soluble transition metal complex, a water-soluble metalhydroxide, a water-soluble metal oxide, and mixtures thereof.

The water-soluble metal cation source may be selected from the groupconsisting of a water-soluble transition metal salt, a water-solublegroup(III) metal salt, and mixtures thereof. According to one embodimentthe water-soluble metal cation source is selected from the groupconsisting of water-soluble salts of aluminium, chromium, manganese,iron, cobalt, nickel, copper, zinc, silver, gold, zirconium, palladium,platinum, and mixtures thereof.

Examples of a suitable water-soluble aluminium salts are aluminiumchloride (AlCl₃) or aluminium sulphate (Al₂(SO₄)₃). The water-solublealuminium salt may be an anhydrous salt or a hydrate salt.

Examples of a suitable water-soluble chromium salt are chromium bromide(CrBr₃), chromium chloride (CrCl₂), chromium fluoride (CrF₂), chromiumnitrate (Cr(NO₃)₃), or chromium perchlorate (Cr(ClO₄)₃). Thewater-soluble chromium salt may be an anhydrous salt or a hydrate salt.

Examples of a suitable water-soluble manganese salt are manganesebromide (MnBr₂), manganese chloride (MnCl₂), manganese nitrate(Mn(NO₃)₂), manganese sulphate (MnSO₄), manganese carbonate (MnCO₃),manganese(II) acetate, manganese(II) benzoate, manganese(II) formate,manganese(II) tartrate, or manganese(II) phosphate. The water-solublemanganese salt may be an anhydrous salt or a hydrate salt.

Examples of a suitable water-soluble iron salt are iron bromide (FeBr₂),iron chloride (FeCl₂, FeCl₃), iron iodide (FeI₂), iron nitrate(Fe(NO₃)₃), potassium hexacyanoferrate (K₄Fe(CN)₆), ammonium ironsulphate (NH₄)₂Fe(SO₄)₂, or iron sulphate (FeSO₄). The water-solubleiron salt may be an anhydrous salt or a hydrate salt.

Examples of a suitable water-soluble cobalt salt are cobalt bromide(CuBr₂), cobalt chloride (CoCl₂), cobalt chlorate (Co(ClO₃)₂), cobaltiodide (CoI₂), cobalt nitrate (Co(NO₃)₂), or cobalt sulphate (CoSO₄).The water-soluble cobalt salt may be an anhydrous salt or a hydratesalt.

Examples of a suitable water-soluble copper salt are copper bromide(CuBr₂), copper chloride (CuCl₂), copper nitrate (Cu(NO₃)₂), copperacetate (C₄H₆CuO₄), copper sulphate (CuSO₄), or copper iodide (CuI₂).The water-soluble copper salt may be an anhydrous salt or a hydratesalt.

Examples of a suitable water-soluble zinc salt are zinc bromide (ZnBr₂),zinc chloride (ZnCl₂), zinc nitrate (Zn(NO₃)₂), zinc iodide (ZnI₂), zincsulphate, zinc(II) acetate, or zinc(II) citrate. The water-soluble zincsalt may be an anhydrous salt or a hydrate salt.

Examples of suitable water-soluble silver salts are silver perchlorate(AgClO₄) and silver nitrate (AgNO₃). The water-soluble silver salt maybe an anhydrous salt or a hydrate salt.

Examples of a suitable water-soluble gold salts are gold(III) bromide,gold(III) chloride, or potassium dicyanoaurate(I) (K[Au(CN)₂]). Thewater-soluble gold salt may be an anhydrous salt or a hydrate salt.

An example of a suitable water-soluble zirconium salt is zirconium(IV)sulphate. The water-soluble zirconium salt may be an anhydrous salt or ahydrate salt.

Examples of suitable water-soluble palladium salts are palladium(II)sulphate, palladium(II) nitrate, tetraammine palladium hydrogencarbonate, or diamine dichloro palladium(II). The water-solublepalladium salt may be an anhydrous salt or a hydrate salt.

Examples of a suitable water-soluble platinum salts are platinum(IV)bromide, platinum(IV) chloride, Na₂PtCl₆, or H₂PtCl₆. The water-solubleplatinum salt may be an anhydrous salt or a hydrate salt.

As used herein, a “hydrate” is an inorganic salt containing watermolecules combined in a definite ratio as an integral part of thecrystal. Depending on the number of water molecules per formula unit ofsalt, the hydrate may be designated as monohydrate, dihydrate,trihydrate, tetrahydrate, pentahydrate, hexahydrate, heptahydrate,octahydrate, nonahydrate, decahydrate, hemihydrates, etc.

Examples of water-soluble transition metal complexes are Na₂PdCl₄,Na₂PtCl₄, Pd(OAc)₂, Pd(H₂NCH₂CH₂NH₂)Cl₂, PdCl₂.

Water-soluble metal hydroxides or water-soluble metal oxides may also bea suitable metal cation source.

According to a preferred embodiment the water-soluble metal cationsource is a water-soluble salt of copper and/or zinc, and morepreferably the water-soluble metal cation source is selected from thegroup consisting of copper nitrate, copper sulphate, copper acetate,copper chloride, copper bromide, copper iodide, zinc nitrate, zincsulphate, zinc acetate, zinc chloride, zinc bromide, zinc iodide,hydrates thereof, and mixtures thereof.

According to one embodiment the at least one water-soluble metal cationsource is provided in an amount from 0.01 to 60 wt.-%, based on thetotal weight of the calcium carbonate-comprising material, preferablyfrom 0.05 to 50 wt.-%, more preferably from 0.1 to 25 wt.-%, and mostpreferably from 0.5 to 10 wt.-%. According to an exemplary embodiment,the at least one water-soluble metal cation source is provided in anamount from 1 to 10 wt.-%, based on the total weight of the calciumcarbonate-comprising material, preferably from 2 to 8 wt.-%, morepreferably from 3 to 6 wt.-%, and most preferably from 4 to 5 wt.-%.

The at least one water soluble metal salt, water soluble metalhydroxide, water soluble metal oxide or mixtures thereof can be providedin form of a solution, a suspension or as a dry material.

According to one embodiment the at least one water soluble metal salt,water soluble metal hydroxide, water soluble metal oxide or mixturesthereof is provided as dry material. The dry material may be in the formof powder, flakes, granules etc. and most preferably is in the form of apowder.

According to another embodiment the at least one water-soluble metalcation source is provided in form of an aqueous solution or aqueoussuspension, preferably an aqueous solution, comprising the at least onewater-soluble metal cation source in an amount from 0.01 to 10 wt.-%,based on the total weight of the aqueous solution, preferably in anamount from 0.1 to 8 wt.-%, more preferably in an amount from 0.4 to 5wt.-%, and most preferably in an amount from 0.8 to 2 wt.-%.

Process Step d)

According to step d) of the process of the present invention, thecalcium carbonate-comprising material of step a) is treated with the atleast one H₃O⁺ ion donor of step b) and carbon dioxide in an aqueousmedium to form a suspension of surface-reacted calcium carbonate,wherein the carbon dioxide is formed in-situ by the H₃O⁺ ion donortreatment and/or is supplied from an external source, and wherein the atleast one water-soluble metal cation source of step c) is added duringstep d).

The calcium carbonate-comprising material can be treated with the atleast one H₃O⁺ ion donor by providing an aqueous suspension of thecalcium carbonate-comprising material and adding the at least one H₃O⁺ion donor to said suspension. The at least one H₃O⁺ ion donor can beadded to the suspension as a concentrated solution or a more dilutedsolution. As an alternative, it is also possible to treat the calciumcarbonate-comprising material with the at least one H₃O⁺ ion donor byadding the calcium carbonate-comprising material to a solution of the atleast one H₃O⁺ ion donor.

The least one H₃O⁺ ion donor of step b) and the at least onewater-soluble metal cation source of step c) may be provided in form ofseparate solutions and/or in form of combined solutions.

According to one embodiment, in step d) the calcium carbonate-comprisingmaterial is treated with a solution comprising the at least one H₃O⁺ iondonor of step b) and the at least one water-soluble metal cation sourceof step c).

According to another embodiment, in step d) the calciumcarbonate-comprising material is treated with a first solutioncomprising a first part of the at least one H₃O⁺ ion donor of step b),and subsequently, with a second solution comprising the remaining partof the at least one H₃O⁺ ion donor of step b) and the at least onewater-soluble metal cation source of step c). The first solution maycomprise less than or equal to 50 wt.-% of the at least one H₃O⁺ iondonor, based on the total amount of the at least one H₃O⁺ ion donor,preferably less than or equal to 40 wt.-%, more preferably less than orequal to 30 wt.-%, and most preferably less than or equal to 20 wt.-%.For example, the first solution may comprise from 0.1 to 50 wt.-% of theat least one H₃O⁺ ion donor, based on the total amount of the at leastone H₃O⁺ ion donor, preferably from 1 to 40 wt.-%, more preferably from5 to 30 wt.-%, and most preferably from 10 to 20 wt.-%.

According to still another embodiment, in step b) a first H₃O⁺ ion donorand a second H₃O⁺ ion donor are provided, and in step d) the calciumcarbonate-comprising material is treated with a first solutioncomprising the first H₃O⁺ ion donor, and subsequently, with a secondsolution comprising the second H₃O⁺ ion donor and the at least onewater-soluble metal cation source of step c).

According to one embodiment in step d) the calcium carbonate-comprisingmaterial is treated with a first solution comprising a first part of theat least one H₃O⁺ ion donor of step b), and subsequently, with a secondsolution comprising the remaining part of the at least one H₃O⁺ iondonor of step b) and the at least one water-soluble metal cation sourceof step c), wherein the first solution comprises less than 50 wt.-% ofthe at least one H₃O⁺ ion donor, based on the total amount of the atleast one H₃O⁺ ion donor, preferably less than 40 wt.-%, more preferablyless than 30 wt.-%, and most preferably less than 20 wt.-%.

According to a preferred embodiment in step d) the calciumcarbonate-comprising material is treated with a solution comprising theat least one H₃O⁺ ion donor in an amount from 1 to 80 wt.-%, preferablyin an amount from 2 to 50 wt.-%, more preferably in an amount from 5 to30 wt.-%, and most preferably in an amount from 10 to 20 wt.-%, based onthe total weight of the aqueous solution, and the at least onewater-soluble metal cation source in an amount from 0.01 to 10 wt.-%,preferably in an amount from 0.1 to 8 wt.-%, more preferably in anamount from 0.4 to 5 wt.-%, and most preferably in an amount from 0.8 to2 wt.-%, based on the total weight of the aqueous solution.

According to a preferred embodiment, the calcium carbonate-comprisingmaterial is a natural ground calcium carbonate, the at least one H₃O⁺ion donor is phosphoric acid, the at least one water-soluble metalcation source is selected from the group consisting of copper nitrate,copper sulphate, copper acetate, copper chloride, copper bromide, copperiodide, zinc nitrate, zinc sulphate, zinc acetate, zinc chloride, zincbromide, zinc iodide, hydrates thereof, and mixtures thereof, and instep d) the calcium carbonate-comprising material is treated with asolution comprising the at least one H₃O⁺ ion donor of step b) and theat least one water-soluble metal cation source of step c).

According to a preferred embodiment, the calcium carbonate-comprisingmaterial is a natural ground calcium carbonate, the at least one H₃O⁺ion donor is phosphoric acid, the at least one water-soluble metalcation source is selected from the group consisting of copper nitrate,copper sulphate, copper acetate, copper chloride, copper bromide, copperiodide, zinc nitrate, zinc sulphate, zinc acetate, zinc chloride, zincbromide, zinc iodide, hydrates thereof, and mixtures thereof, and instep d) the calcium carbonate-comprising material is treated with afirst solution comprising a first part of the at least one H₃O⁺ iondonor of step b), and subsequently, with a second solution comprisingthe remaining part of the at least one H₃O⁺ ion donor of step b) and theat least one water-soluble metal cation source of step c).

According to one embodiment, the at least one H₃O⁺ ion donor is addedover a time period of at least 1 min, preferably at least 5 min, andmore preferably at least 10 min. In case the calciumcarbonate-comprising material is treated with a first and a secondsolution, the first solution comprising a first part of the at least oneH₃O⁺ ion donor or a first H₃O⁺ ion donor may be added over a time periodof at least 1 min, preferably at least 5 min, and more preferably atleast 10 min, and the second solution comprising the remaining part ofthe at least one H₃O⁺ ion donor or the second H₃O⁺ ion donor and the atleast one water-soluble metal cation source may be added over a timeperiod of at least 1 min, preferably at least 5 min, and more preferablyat least 10 min.

According to step d) of the process of the present invention, thecalcium carbonate-comprising material is treated with carbon dioxide. Ifa strong acid such as sulphuric acid or hydrochloric acid is used forthe H₃O⁺ ion donor treatment of the calcium carbonate-comprisingmaterial, the carbon dioxide is automatically formed. Alternatively oradditionally, the carbon dioxide can be supplied from an externalsource.

H₃O⁺ ion donor treatment and treatment with carbon dioxide can becarried out simultaneously which is the case when a strong ormedium-strong acid is used. It is also possible to carry out H₃O⁺ iondonor treatment first, e.g. with a medium strong acid having a pK_(a) inthe range of 0 to 2.5 at 20° C., wherein carbon dioxide is formed insitu, and thus, the carbon dioxide treatment will automatically becarried out simultaneously with the H₃O⁺ ion donor treatment, followedby the additional treatment with carbon dioxide supplied from anexternal source.

Preferably, the concentration of gaseous carbon dioxide in thesuspension formed in step d) is, in terms of volume, such that the ratio(volume of suspension):(volume of gaseous CO₂) is from 1:0.05 to 1:20,even more preferably 1:0.05 to 1:5.

In a preferred embodiment, the H₃O⁺ ion donor treatment step and/or thecarbon dioxide treatment of step d) are repeated at least once, morepreferably several times.

Subsequent to the H₃O⁺ ion donor treatment and carbon dioxide treatment,the pH of the aqueous suspension, measured at 20° C., naturally reachesa value of greater than 6.0, preferably greater than 6.5, morepreferably greater than 7.0, even more preferably greater than 7.5,thereby preparing the surface-reacted natural or precipitated calciumcarbonate as an aqueous suspension having a pH of greater than 6.0,preferably greater than 6.5, more preferably greater than 7.0, even morepreferably greater than 7.5.

According to one embodiment of the present invention, step d) is carriedout at a temperature from 20 to 90° C., preferably from 30 to 85° C.,more preferably from 40 to 80° C., even more preferably from 50 to 75°C., and most preferably from 60 to 70° C.

According to one embodiment, the process step d) is carried out for atleast 1 min, preferably for at least 5 min, more preferably for at least10 min, and most preferably for at least 15 min.

Process step d) may be carried out by simply adding, for example, bypouring, discharging, or injecting, the at least one H₃O⁺ ion donorand/or the at least one water-soluble metal cation source into thecalcium carbonate-comprising material. According to one embodiment,process step d) is carried out under mixing conditions. Suitable mixingmethods are known to the skilled person. Examples of suitable mixingmethods are shaking, mixing, stirring, agitating, ultrasonication, orinducing a turbulent or laminar flow by means such as baffles orlamellae. Suitable mixing equipment is known to the skilled person, andmay be selected, for example, from stirrers, such as rotor statorsystems, blade stirrers, propeller stirrers, turbine stirrers, or anchorstirrers, static mixers such as pipes including baffles or lamellae.According to an exemplary embodiment of the present invention, a rotorstator stirrer system is used.

According to another exemplary embodiment, in step d) the formedsuspension is mixed so as to develop an essentially laminar flow. Theskilled person will adapt the mixing conditions such as the mixing speedand temperature according to his process equipment.

Depending on the amount of water that is introduced during step d) bycontacting the aforementioned compounds, additional water may beintroduced during process step d), for example, in order to controland/or maintain and/or achieve the desired solids content or Brookfieldviscosity of the obtained aqueous suspension. According to oneembodiment the solids content of the mixture obtained in step d) is from5 to 80 wt.-%, preferably from 20 to 78 wt.-%, based on the total weightof the mixture. The Brookfield viscosity of the obtained aqueoussuspension may be from 10 to 10 000 mPa·s, preferably from 50 to 1 000mPa·s.

The process of the present invention may be carried out in form of acontinuous process or a batch process, preferably in from of acontinuous process.

Additional Process Steps

According to one embodiment, the process of the present inventionfurther comprises a step of agitating the aqueous suspension after stepd). Preferably, the suspension is agitated for at least 1 min,preferably for at least 5 min, more preferably for at least 10 min, andmost preferably for at least 15 min.

The aqueous suspension of surface-reacted calcium carbonate may befurther processed, e.g., the surface-reacted calcium carbonate may beseparated from the aqueous suspension and/or subjected to a drying step.

According to one embodiment, the process of the present inventionfurther comprises a step e) of separating the surface-reacted calciumcarbonate from the aqueous suspension obtained in step d). Thus, aprocess for manufacturing a surface-reacted calcium carbonate maycomprise the following steps:

-   -   a) providing a calcium carbonate-comprising material,    -   b) providing at least one H₃O⁺ ion donor,    -   c) providing at least one water-soluble metal cation source, and    -   d) treating the calcium carbonate-comprising material of step a)        with the at least one H₃O⁺ ion donor of step b) and carbon        dioxide in an aqueous medium to form an aqueous suspension of        surface-reacted calcium carbonate,    -   wherein the carbon dioxide is formed in-situ by the H₃O⁺ ion        donor treatment and/or is supplied from an external source, and    -   wherein the at least one water-soluble metal cation source of        step c) is added during step d), and    -   e) separating the surface-reacted calcium carbonate from the        aqueous suspension obtained from step d).

The surface-reacted calcium carbonate obtained from step d) may beseparated from the aqueous suspension by any conventional means ofseparation known to the skilled person. According to one embodiment ofthe present invention, in process step e) the surface-reacted calciumcarbonate is separated mechanically and/or thermally. Examples ofmechanical separation processes are filtration, e.g. by means of a drumfilter or filter press, nanofiltration, or centrifugation. An examplefor a thermal separation process is a concentrating process by theapplication of heat, for example, in an evaporator. According to apreferred embodiment, in process step e) the surface-reacted calciumcarbonate is separated mechanically, preferably by filtration and/orcentrifugation.

After separation, the surface-reacted calcium carbonate can be dried inorder to obtain a dried surface-reacted calcium carbonate. According toone embodiment, the process of the present invention further comprises astep f) of drying the surface-reacted calcium carbonate after step d) orafter step e), if present, at a temperature in the range from 60 to 600°C., preferably until the moisture content of the surface-reacted calciumcarbonate is between 0.01 and 5 wt.-%, based on the total weight of thedried surface-reacted calcium carbonate.

According to one embodiment of the present invention, a process formanufacturing a dried surface-reacted calcium carbonate is providedcomprising the following steps:

-   -   a) providing a calcium carbonate-comprising material,    -   b) providing at least one H₃O⁺ ion donor,    -   c) providing at least one water-soluble metal cation source, and    -   d) treating the calcium carbonate-comprising material of step a)        with the at least one H₃O⁺ ion donor of step b) and carbon        dioxide in an aqueous medium to form an aqueous suspension of        surface-reacted calcium carbonate,    -   wherein the carbon dioxide is formed in-situ by the H₃O⁺ ion        donor treatment and/or is supplied from an external source, and    -   wherein the at least one water-soluble metal cation source of        step c) is added during step d),    -   e) separating the surface-reacted calcium carbonate from the        aqueous suspension obtained from step d), and    -   f) drying the surface-reacted calcium carbonate.

In general, the drying step f) may take place using any suitable dryingequipment and can, for example, include thermal drying and/or drying atreduced pressure using equipment such as an evaporator, a flash drier,an oven, a spray drier and/or drying in a vacuum chamber. The dryingstep f) can be carried out at reduced pressure, ambient pressure orunder increased pressure. For temperatures below 100° C. it may bepreferred to carry out the drying step under reduced pressure.

According to one preferred embodiment, the separation is carried out bya thermal method. This may allow to dry the surface-reacted calciumcarbonate subsequently without changing the equipment.

According to one embodiment, in process step f) the surface-reactedcalcium carbonate is dried until the moisture content of the formedsurface-reacted calcium carbonate is less than or equal to 1.0 wt.-%,based on the total weight of the dried surface-reacted calciumcarbonate, preferably less than or equal to 0.5 wt.-%, and morepreferably less than or equal to 0.2 wt.-%. According to anotherembodiment, in process step d) the surface-reacted calcium carbonate isdried until the moisture content of the formed surface-reacted calciumcarbonate is between 0.01 and 0.15 wt.-%, preferably between 0.02 and0.10 wt.-%, and more preferably between 0.03 and 0.07 wt.-%, based onthe total weight of the dried surface-reacted calcium carbonate.

The Surface-Reacted Calcium Carbonate

According to a further aspect of the present invention, asurface-reacted calcium carbonate is provided, wherein thesurface-reacted calcium carbonate is obtainable by a process of thepresent invention. Thus, the surface-reacted calcium carbonate may beobtained by a process comprising the steps of:

-   -   a) providing a calcium carbonate-comprising material,    -   b) providing at least one H₃O⁺ ion donor,    -   c) providing at least one water-soluble metal cation source, and    -   d) treating the calcium carbonate-comprising material of step a)        with the at least one H₃O⁺ ion donor of step b) and carbon        dioxide in an aqueous medium to form an aqueous suspension of        surface-reacted calcium carbonate, wherein the carbon dioxide is        formed in-situ by the H₃O⁺ ion donor treatment and/or is        supplied from an external source, and    -   wherein the at least one water-soluble metal cation source of        step c) is added during step d).

The surface-reacted calcium carbonate may have different particleshapes, such as e.g. the shape of roses, golf balls and/or brains.

According to one embodiment the surface-reacted calcium carbonate has aspecific surface area of from 15 m²/g to 200 m²/g, preferably from 20m²/g to 180 m²/g, more preferably from 25 m²/g to 160 m²/g, even morepreferably from 27 m²/g to 150 m²/g, most preferably from 30 m²/g to 140m²/g, measured using nitrogen and the BET method. For example, thesurface-reacted calcium carbonate may have a specific surface area offrom 27 m²/g to 100 m²/g, measured using nitrogen and the BET method.The BET specific surface area in the meaning of the present invention isdefined as the surface area of the particles divided by the mass of theparticles. As used therein the specific surface area is measured byadsorption using the BET isotherm (ISO 9277:1995) and is specified inm²/g.

According to one embodiment, the surface-reacted calcium carbonate has avolume determined median particle size d₅₀(vol) from 1 to 75 μm,preferably from 2 to 50 μm, more preferably from 3 to 40 μm, even morepreferably from 4 to 30 μm, and most preferably from 5 to 15 μm, and/ora volume determined top cut particle size d₉₈(vol) from 2 to 150 μm,preferably from 4 to 100 μm, more preferably from 6 to 80 μm, even morepreferably from 8 to 60 μm, and most preferably from 10 to 30 μm.

The surface-reacted calcium carbonate may have an intra-particleintruded specific pore volume in the range from 0.1 to 2.3 cm³/g,preferably from 0.2 to 2.0 cm³/g, more preferably from 0.4 to 1.8 cm³/gand most preferably from 0.6 to 1.6 cm³/g, calculated from mercuryporosimetry measurement.

The intra-particle pore size of the surface-reacted calcium carbonatepreferably is in a range of from 0.004 to 1.6 μm, more preferably in arange of between 0.005 to 1.3 μm, especially preferably from 0.006 to1.15 μm and most preferably of 0.007 to 1.0 μm, e.g. 0.1 to 0.6 μmdetermined by mercury porosimetry measurement.

According to one embodiment, a surface-reacted calcium carbonate isprovided, wherein the surface-reacted calcium carbonate comprises acalcium carbonate-comprising material, at least one water-insolublecalcium salt other than calcium carbonate, and at least onewater-insoluble metal cation salt. According to one embodiment thesurface-reacted calcium carbonate comprises

-   -   (i) a specific surface area of from 15 to 200 m²/g measured        using nitrogen and the BET method according to ISO 9277:2010;    -   (ii) an intra-particle intruded specific pore volume in the        range of from 0.1 to 2.3 cm³/g calculated from mercury        porosimetry measurement; and    -   (iii) a ratio of the at least one water-insoluble calcium salt        to calcium carbonate in the range of from 1:99 to 99:1 by        weight, and    -   (iv) a ratio of the at least one water-insoluble metal cation        salt to calcium carbonate in the range of from 0.00001:1 to        0.1:1 by weight.

According to one embodiment the at least one water-insoluble calciumsalt is selected from the group consisting of octacalcium phosphate,hydroxyapatite, chlorapatite, fluorapatite, carbonate apatite,preferably the at least one water-insoluble calcium salt ishydroxyapatite. According to a further embodiment, the ratio of the atleast one water-insoluble calcium salt to calcium carbonate, preferablycalcite, aragonite and/or vaterite, is in the range of from 1:9 to 9:1,preferably from 1:7 to 8:1, more preferably from 1:5 to 7:1, and evenmore preferably from 1:4 to 7:1 by weight. According to an exemplaryembodiment, the surface-reacted calcium carbonate comprises a ratio ofhydroxyapatite to calcite in the range of from 1:99 to 99:1 by weight,preferably in the range of from 1:9 to 9:1 by weight.

According to one embodiment, the ratio of the at least onewater-insoluble metal cation salt to calcium carbonate, preferablycalcite, aragonite and/or vaterite, is in the range of from 0.0001:1 to0.1:1 by weight, and preferably from 0.001 to 0.01 by weight.

The surface-reacted calcium carbonate obtainable by a process of thepresent invention can be provided in form of a suspension ofsurface-reacted calcium carbonate, as a separated surface-reactedcalcium carbonate or as a dried surface-reacted calcium carbonate.According to a preferred embodiment surface-reacted calcium carbonate isa dried surface-reacted calcium carbonate.

In case the surface-reacted calcium carbonate has been dried, themoisture content of the dried surface-reacted calcium carbonate can bebetween 0.01 and 5 wt.-%, based on the total weight of the driedsurface-reacted calcium carbonate. According to one embodiment, themoisture content of the dried surface-reacted calcium carbonate is lessthan or equal to 1.0 wt.-%, based on the total weight of the driedsurface-reacted calcium carbonate, preferably less than or equal to 0.5wt.-%, and more preferably less than or equal to 0.2 wt.-%. According toanother embodiment, the moisture content of the dried surface-reactedcalcium carbonate is between 0.01 and 0.15 wt.-%, preferably between0.02 and 0.10 wt.-%, and more preferably between 0.03 and 0.07 wt.-%,based on the total weight of the dried surface-reacted calciumcarbonate.

The inventive surface-reacted calcium carbonate may also be providedand/or used in form of a composition. According to one aspect of thepresent invention, a composition is provided comprising asurface-reacted calcium carbonate according to present invention. Saidcomposition may further comprise an additional surface-reacted calciumcarbonate, wherein the additional surface-reacted calcium carbonate is areaction product of natural ground calcium carbonate or precipitatedcalcium carbonate with carbon dioxide and at least one H₃O ion donor,wherein the carbon dioxide is formed in-situ by the H₃O⁺ ion donortreatment and/or is supplied from an external source. Alternatively, oradditionally other filler materials such as natural ground calciumcarbonate, precipitated calcium carbonate, dolomite, and mixturesthereof may be present. The composition may comprise the surface-reactedcalcium carbonate according to present invention in an amount of atleast 20 wt.-%, based on the total weight of the composition, preferablyat least 40 wt.-%, more preferably at least 60 wt.-%, and mostpreferably at least 80 wt.-%.

The following paragraphs are intended to refer to the aqueous suspensionof surface-reacted calcium carbonate, the separated surface-reactedcalcium carbonate as well as the dried surface-reacted calciumcarbonate.

The inventors surprisingly found that by the inventive process asurface-reacted calcium carbonate is formed which provides additionalfunctionalities due to the incorporation of metal cations into thestructure of the surface-reacted calcium carbonate. It was found thatsaid functionalities can be tailored for the desired application byselecting an appropriate water-soluble metal cation source.

For example, the inventors of the present invention found that thesurface-reacted calcium carbonate may exhibit antimicrobial activity indry products or wet products, preferably dry products. Therefore, theinventive surface-reacted calcium carbonate can be used in suspensions,dispersions or slurries of minerals, fillers or pigments, which aretypically employed in the paper, paint, rubber and plastics industriesas coatings, fillers, extenders and pigments for papermaking as well asaqueous lacquers and paints intended for the preparation of dry or wetproducts, wherein the dry products are preferred. The inventivesurface-reacted calcium carbonate may also substitute conventionalfillers completely or partially. Since both the surface-reacted calciumcarbonate is resistant to water, a long lasting antimicrobial effect canbe provided by the inventive surface-reacted calcium carbonate. Thus,the inventive surface-reacted calcium carbonate can even be used inarticles, which involve contact with water or aqueous liquids or aresubjected regularly to water washing, such as paints or cloths.

Moreover, it was found that the inventive surface-reacted calciumcarbonate may release minor amounts of metal cations, i.e. in the ppmrange, and thus, may be used as micronutrient delivery agent and plantprotection product on the same time. For example, in case the metalcation is copper the surface-reacted calcium carbonate may be used toreplace conventional plant protection products such as the Bordeauxmixture used in vineyard treatments.

According to one embodiment, the inventive surface-reacted calciumcarbonate is used as metal cation releaser, preferably as micronutrientdelivery agent and/or plant protection product.

The surface-reacted calcium carbonate may be used for variousapplications.

According to one embodiment, the surface-reacted calcium carbonateobtainable by a process according to the present invention or acomposition comprising the same is used in polymer applications, papercoating applications, paper making, paints, coatings, sealants, printinginks, adhesives, food, feed, pharmaceuticals, concrete, cement,cosmetics, water treatment, engineered wood applications, plasterboardapplications, packaging applications and/or agricultural applications.Engineered wood applications may comprise the use in engineered woodproducts such as wood composites materials, preferably medium densityfibreboards or chipboards. Preferably the surface-reacted calciumcarbonate may be used as a dried surface-reacted calcium carbonate.

According to another embodiment, the surface-reacted calcium carbonateobtainable by a process according to the present invention or acomposition comprising the same is used as preservative, for the controlof odour, and/or for enhancing and/or mediating antimicrobial activityof a substrate. Preferably the surface-reacted calcium carbonate may beused as a dried surface-reacted calcium carbonate.

A preservative is a compound which can protect a substrate, dry and/orwet, from spoilage and/or degradation and/or destruction, and/ordefacement and/or visible disfigurement due to the action ofmicroorganisms and/or prevent growth of microorganisms on a substrateand/or in a substrate and/or prevent contamination of a substrate bymicroorganisms and/or prevent settlement of microorganisms on ansubstrate. According to a preferred embodiment, the preservative acts asa dry-film-preservative. The substrate is preferably in a solid state,such as a paper surface, a wood surface, a wall, the surface of apackaging material or the surface of a polymer article, but can also bein a wet state such as in an aqueous suspension.

“Odour” according to the present invention generally is defined as oneor more volatilized chemical compounds, generally at a very lowconcentration, that humans or other animals perceive by the sense ofolfaction. Accordingly, an “odorant” is a chemical compound that has asmell or odour, i.e. is sufficiently volatile to be transported to theolfactory system in the upper part of the nose.

Preferred odours to be controlled according to the present invention areodours which cause an unpleasant sensation, i.e. malodours, but are notlimited thereto. Such odours may originate from odorants, which arepreferably selected from the group comprising odorants contained inhuman and animal body liquids and secretion such as menses, blood,plasma, sanies; vaginal secretions, mucus, milk, urine; faeces; vomitand perspiration; odorants originating from putrefaction such as ofhuman or animal tissue; food such as dairy products, meat and fish andfruit such as durian fruit.

According to one preferred embodiment of the present invention theodorants are selected from the group consisting of amines such astriethylamine, diethylamine, trimethylamine, diaminobutane,tetramethylenediamine, pentamethylenediamine, pyridine, indole,3-methylindole; carboxylic acids such as propionic acid, butanoic acid,3-methylbutanoic acid, 2-methylpropanoic acid, hexanoic acid; sulphurorganic compounds such as thiols, e.g. methanethiol, phosphor organiccompounds such as methylphosphine, dimethylphosphine, their derivativesand mixtures thereof; preferably the odorants are amines and mostpreferably the odorant is diethylamine. According to an exemplifiedembodiment of the present invention the odourants are diethylamine or athiol, for example 2-propanethiol.

The surface-reacted calcium carbonate can also be used for enhancingand/or mediating the antimicrobial activity of a substrate, e.g. a sheetof paper, a cardboard, a polymer material, a paint, a wood surface,concrete, or a plant. According to a preferred embodiment, theantimicrobial activity is against at least one strain of bacteria and/orat least one strain of mould and/or at least one strain of yeast and/orat least one algae. Antimicrobial activity of a compound refers to areduction of growth of microorganism and/or a reduction of viablemicroorganisms apparent in the presence of said compound. The expression“enhancing the antimicrobial activity” means that the antimicrobialactivity of the substrate containing the inventive surface-reactedcalcium carbonate is higher than the antimicrobial activity compared toa substrate not containing said filler. The expression “for mediatingthe antimicrobial activity of a substrate” means that no antimicrobialactivity is apparent in a substrate without the inventivesurface-reacted calcium carbonate.

According to one embodiment, the substrate is a paper, a cardboard, apolymer material, a paint, a wood surface, concrete, or a plant.According to one embodiment, the polymer material is a polymer film. A“film” in the meaning of the present invention is a sheet or layer ofmaterial having a median thickness which is small compared to its lengthand width. For example, the term “film” may refer to a sheet or layer ofmaterial having a median thickness of less than 200 μm, but more than 1μm.

According to one embodiment the at least one strain of bacteria isselected from the group consisting of Escherichia sp., Staphylococcussp., Thermus sp., Propionibacterium sp., Rhodococcus sp., Panninobactersp., Caulobacter sp., Brevundimonas sp., Asticcacaulis sp., Sphingomonassp., Rhizobium sp., Ensifer sp., Bradyrhizobium sp., Tepidimonas sp.,Tepidicella sp., Aquabacterium sp., Pelomonas sp., Alcaligenis sp.,Achromobacter sp., Ralstonia sp., Limnobacter sp., Massilia sp.,Hydrogenophaga sp., Acidovorax sp., Curvibacter sp., Delftia sp.,Rhodoferax sp., Alishewanella sp., Stenotrophomonas sp., Dokdonella sp.,Methylo sinus sp., Hyphomicrobium sp., Methylosulfomonas sp.,Methylobacteria sp., Pseudomonas sp. such as Pseudomonas mendocina,Enterococcus sp., Myroides sp., Burkholderia sp., Alcaligenes sp.Staphylococcus sp. such as Staphylococcus aureus, Escherichia sp. suchas Escherichia coli, and mixtures thereof.

According to one embodiment the at least one strain of mould is selectedfrom the group comprising of Acremonium sp., Alternaria sp., Aspergillussp. such as Aspergillus niger, Aureobasidium sp., such as Aureobasidiumpullulans, Cladosporium sp., Fusarium sp., Mucor sp., Penicillium sp.,such as Penicillium funiculosum, Rhizopus sp., Stachybotrys sp.,Trichoderma sp., Dematiaceae sp., Phoma sp., Eurotium sp.,Scopulariopsis sp., Aureobasidium sp., Monilia sp., Botrytis sp.,Stemphylium sp., Chaetomium sp., Mycelia sp., Neurospora sp., Ulocladiumsp., Paecilomyces sp., Wallemia sp., Curvularia sp., and mixturesthereof.

According to one embodiment the at least one strain of yeast is selectedfrom the group comprising Saccharomycotina, Taphrinomycotina,Schizosaccharomycetes, Basidiomycota, Agaricomycotina, Tremellomycetes,Pucciniomycotina, Microbotryomycetes, Candida sp. such as Candidaalbicans, Candida tropicalis, Candida stellatoidea, Candida glabrata,Candida krusei, Candida guilliermondii, Candida viswanathii, Candidalusitaniae and mixtures thereof, Yarrowia sp. such as Yarrowialipolytica, Cryptococcus sp. such as Cryptococcus gattii andCryptococcus neofarmans, Zygosaccharomyces sp., Rhodotorula sp. such asRhodotorula mucilaginosa, and mixtures thereof.

According to a preferred embodiment of the present invention, the atleast one strain of bacteria is selected from the group consisting ofEscherichia coli, Staphylococcus aureus, Pseudomonas putida, Pseudomonasmendocina, Pseudomonas oleovorans, Pseudomonas fluorescens, Pseudomonasalcaligenes, Pseudomonas pseudoalcaligenes, Pseudomonas entomophila,Pseudomonas syringae, Methylobacterium extorquens, Methylobacteriumradiotolerants, Methylobacterium dichloromethanicum, Methylobacteriumorganophilu, Hyphomicrobium zavarzini, Enterococcus faecalis, Myroidesodoratus, Pseudomonas aeruginosa, Pseudomonas orizyhabitans,Burkholderia cepacia, Alcaligenes faecalis and Sphingomonas paucimobilisand mixtures thereof and/or the at least one strain of mould is selectedfrom the group comprising of Penicillium funiculosum, Aspergillus niger,Aureobasidium pullulans, Alternaria alternate, Cladosporiumcladosporioides, Phoma violaceae, Ulocladium atrum, Aspergillusversicolor, Stachybotris chartarum, Penicillium purpurogenum,Rhodotorula mucilaginosa and/or the at least one strain of yeast isselected from the group of Candida albicans and/or the at least onestrain of alga is selected from the group of Nostoc commune, Gloeocapsaalpicola (syn. Anacystis montana), Klebsormidium flaccidum, Stichococcusbacillaris, Pseudokirchneriella subcapitata, Desmodesmus subspicatus,Navicula pelliculosa, Anabaena flosaquae, Synechococcus leopoliensis,and mixtures thereof.

According to still another embodiment, the surface-reacted calciumcarbonate obtained by the process of the present invention is used forenhancing the electrical conductivity of a substrate.

The inventive surface-reacted calcium carbonate may be incorporated intoan article in order to provide an article with enhanced antimicrobialactivity and/or enhanced electrical conductivity. According to a furtheraspect of the present invention, an article is provided comprising asurface-reacted calcium carbonate obtainable by a process according tothe present invention or a composition comprising the same, wherein thearticle is selected from paper products, engineered wood products,plasterboard products, polymer products, hygiene products, medicalproducts, healthcare products, filter products, woven materials,nonwoven materials, geotextile products, agriculture products,horticulture products, clothing, footwear products, baggage products,household products, industrial products, packaging products, buildingproducts, and construction products.

The scope and interest of the invention will be better understood basedon the following examples which are intended to illustrate certainembodiments of the present invention and are non-limitative.

EXAMPLES

1. Measurement Methods

In the following, measurement methods implemented in the examples aredescribed.

Particle Size Distribution

Volume determined median particle size d₅₀(vol) and the volumedetermined top cut particle size d₉₈(vol) was evaluated using a MalvernMastersizer 2000 Laser Diffraction System (Malvern Instruments Plc.,Great Britain). The d₅₀ or d₉₈ value, measured using a MalvernMastersizer 2000 Laser Diffraction System, indicates a diameter valuesuch that 50% or 98% by volume, respectively, of the particles have adiameter of less than this value. The raw data obtained by themeasurement were analysed using the Mie theory, with a particlerefractive index of 1.57 and an absorption index of 0.005.

The weight determined median particle size d₅₀(wt) was measured by thesedimentation method, which is an analysis of sedimentation behaviour ina gravimetric field. The measurement was made with a Sedigraph™ 5100 or5120 of Micromeritics Instrument Corporation, USA. The method and theinstrument are known to the skilled person and are commonly used todetermine particle size distributions of fillers and pigments. Themeasurement was carried out in an aqueous solution of 0.1 wt.-% Na₄P₂O₇.The samples were dispersed using a high speed stirrer andsupersonicated.

Specific Surface Area (SSA)

The specific surface area was measured via the BET method according toISO 9277:2010 using nitrogen, following conditioning of the sample byheating at 100° C. under vacuum for a period of 30 minutes. Prior tosuch measurements, the sample was filtered within a Buchner funnel,rinsed with deionised water and dried overnight at 90 to 100° C. in anoven. Subsequently, the dry cake was ground thoroughly in a mortar andthe resulting powder was placed in a moisture balance at 130° C. until aconstant weight was reached.

Intra-Particle Intruded Specific Pore Volume (In cm³/g)

The specific pore volume was measured using a mercury intrusionporosimetry measurement using a Micromeritics Autopore V 9620 mercuryporosimeter having a maximum applied pressure of mercury 414 MPa (60 000psi), equivalent to a Laplace throat diameter of 0.004 μm (˜nm). Theequilibration time used at each pressure step was 20 seconds. The samplematerial was sealed in a 3 cm³ chamber powder penetrometer for analysis.The data were corrected for mercury compression, penetrometer expansionand sample material compression using the software Pore-Comp (Gane, P.A. C., Kettle, J. P., Matthews, G. P. and Ridgway, C. J., “Void SpaceStructure of Compressible Polymer Spheres and Consolidated CalciumCarbonate Paper-Coating Formulations”, Industrial and EngineeringChemistry Research, 35(5), 1996, p1753-1764.).

The total pore volume seen in the cumulative intrusion data can beseparated into two regions with the intrusion data from 214 μm down toabout 1-4 μm showing the coarse packing of the sample between anyagglomerate structures contributing strongly. Below these diameters liesthe fine inter-particle packing of the particles themselves. If theyalso have intra-particle pores, then this region appears bi-modal, andby taking the specific pore volume intruded by mercury into pores finerthan the modal turning point, i.e. finer than the bi-modal point ofinflection, the specific intra-particle pore volume is defined. The sumof these three regions gives the total overall pore volume of thepowder, but depends strongly on the original sample compaction/settlingof the powder at the coarse pore end of the distribution.

By taking the first derivative of the cumulative intrusion curve thepore size distributions based on equivalent Laplace diameter, inevitablyincluding pore-shielding, are revealed. The differential curves clearlyshow the coarse agglomerate pore structure region, the inter-particlepore region and the intra-particle pore region, if present. Knowing theintra-particle pore diameter range it is possible to subtract theremainder inter-particle and inter-agglomerate pore volume from thetotal pore volume to deliver the desired pore volume of the internalpores alone in terms of the pore volume per unit mass (specific porevolume). The same principle of subtraction, of course, applies forisolating any of the other pore size regions of interest.

Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)

Powder/filter cake were dissolved in HNO₃ (69%, trace select) and boiledfor 3 minutes. After cooling, the solubilized samples were diluted withwater. The solution was then filtered (0.2 μm), and further dilutedprior to analysis.

Aqueous samples were acidified with HNO₃ (69%, trace select), filtered(0.2 μm) and diluted if needed prior to analysis.

Analysis was made by ICP-OES on an Optima 3200 XL device (Copper linesCu 224.7, Cu 324.752, Cu 327.393).

Antimicrobial Surface Activity Test

Fresh bacteria cultures of the bacteria Staphylococcus aureus DSM 346strains were prepared by dilution streaking onto a tryptic soy agarplate (TSA, no. 236950, Becton Dickinson and Company, USA) andincubation for 16 to 20 h at 35° C.

To test the antimicrobial surface activity, the Japanese StandardProtocol JIS Z 2801 2000 was followed using fresh bacteria prepared asdescribed above. The plating, counting and evaluation were doneaccording to the Japanese Standard Protocol JIS Z 2801 2000 with thefollowing amendments. For all coated samples, the bacteria were releasedafter incubation from the test item in a petri dish using a sterileDrigalski spatula to massage the test item with medium, instead of usinga stomacher bag and massaging the item by hand. Further for coatedsamples the test items were not sterilized with 70% ethanol prioranalysis.

As described in the Japanese Standard Protocol JIS Z 2801 2000, thebacterial counts are reported as colony forming units per test item(cfu/test item) with 10 cfu/test item as limit of detection (LOD).Thereof the antimicrobial activity (R) of the test items was calculatedas described in the Japanese Standard Protocol JIS Z 2801 2000. For it,after 24 h incubation at 35° C., the average number of viable bacteriaon the test item (B) and the untreated control (A) are used to calculatethe antimicrobial activity (R) using the following formula:R=log₁₀(A/B). If zero cfu were detected, a value of 10 cfu/test item wasused for calculation of the limit of detection of the antimicrobialactivity.

2. Mineral Materials

Surface-Reacted Calcium Carbonate SRCC 1 (Inventive)

SRCC 1 was obtained by preparing 10 litres of an aqueous suspension ofground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground marble calcium carbonate from Hustadmarmor Norwayhaving a mass based particle size distribution of 90% less than 2 μm, asdetermined by sedimentation, such that a solids content of 10 wt.-%,based on the total weight of the aqueous suspension, is obtained.

In addition a solution was prepared containing 30% by mass phosphoricacid and 1% by mass of copper sulphate pentahydrate, CuSO₄.5H₂O.

Whilst mixing the slurry, 1.1 kg of the phosphoric acid/copper sulphatesolution was added to said suspension over a period of 10 minutes at atemperature of 70° C. Finally, after the addition of the phosphoricacid, the slurry was stirred for additional 5 minutes, before removingit from the vessel. Then, the slurry was dewatered by use of a filterpress (with a maximum pressure of 4 bar) and dried in an oven at atemperature of 120° C. until dry. The obtained surface-reacted calciumcarbonate had the following properties: d₅₀=5.5 μm, d₉₈=8.6 μm, SSA=55.5m²g⁻¹. The intra-particle intruded specific pore volume is 1.150 cm³/g(for the pore diameter range of 0.004 to 0.43 μm).

Surface-Reacted Calcium Carbonate SRCC 2 (Inventive)

SRCC 2 was obtained by preparing 10 litres of an aqueous suspension ofground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground marble calcium carbonate from Hustadmarmor Norwayhaving a mass based particle size distribution of 90% less than 2 μm, asdetermined by sedimentation, such that a solids content of 10 wt.-%,based on the total weight of the aqueous suspension, is obtained.

In addition, two solutions were prepared. Solution A was prepared suchthat it contained 30 wt.-%, based on the total weight of the aqueoussolution, of phosphoric acid. Solution B was prepared by blending coppersulphate pentahydrate, CuSO₄.5H₂O into a solution of phosphoric acidsuch that the final solution contained 28.8 wt.-%, based on the totalweight of the aqueous solution, of phosphoric acid and 1.0 wt.-%, basedon the total weight of the aqueous solution, of copper ion.

Whilst mixing the slurry, 534 g of solution A was added to the 10 wt.-%calcium carbonate suspension over a period of 5 minutes. Directly aftersolution A finished adding, 555 g of solution B was added to thesuspension over a period of 6 minutes. Throughout the whole experimentthe temperature of the suspension was maintained at 70° C. Finally,after the addition of solution B, the suspension was stirred foradditional 5 minutes before removing it from the vessel and drying. Theobtained surface-reacted calcium carbonate had the following properties:d₅₀=5.4 μm, d₉₈ =8.0 μm, and SSA=46.4 m²g⁻¹. The intra-particle intrudedspecific pore volume was 0.98 cm³/g (for the pore diameter range of0.004 to 0.38 μm).

Surface-Reacted Calcium Carbonate SRCC 3 (Inventive)

SRCC 3 was obtained by preparing 10 litres of an aqueous suspension ofground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground marble calcium carbonate from Hustadmarmor Norwayhaving a mass based particle size distribution of 90% less than 2 μm, asdetermined by sedimentation, such that a solids content of 10 wt.-%,based on the total weight of the aqueous suspension, is obtained.

In addition, two solutions were prepared. Solution A was prepared suchthat it contained 30 wt.-%, based on the total weight of the aqueoussolution, of phosphoric acid. Solution B was prepared by blending coppersulphate pentahydrate, CuSO₄.5H₂O into a solution of phosphoric acidsuch that the final solution contained 27.3 wt.-%, based on the totalweight of the aqueous solution, of phosphoric acid and 2.3 wt.-%, basedon the total weight of the aqueous solution, of copper ion.

Whilst mixing the slurry, 534 g of solution A was added to the 10 wt.-%calcium carbonate suspension over a period of 5 minutes. Directly aftersolution A finished adding, 587 g of solution B was added to thesuspension over a period of 6 minutes. Throughout the whole experimentthe temperature of the suspension was maintained at 70° C. Finally,after the addition of solution B, the suspension was stirred foradditional 5 minutes before removing it from the vessel and drying. Theobtained surface-reacted calcium carbonate had the following properties:d₅₀=5.2 μm, d₉₈=8.1 μm, SSA=30.3 m²g⁻¹. The intra-particle intrudedspecific pore volume was 1.00 cm³/g (for the pore diameter range of0.004 to 0.30 μm).

Surface-Reacted Calcium Carbonate SRCC 4 (Inventive)

SRCC 4 was obtained by preparing 10 litres of an aqueous suspension ofground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground marble calcium carbonate from Hustadmarmor Norwayhaving a mass based particle size distribution of 90% less than 2 μm, asdetermined by sedimentation, such that a solids content of 10 wt.-%,based on the total weight of the aqueous suspension, is obtained.

In addition, two solutions were prepared. Solution A was prepared suchthat it contained 30 wt.-%, based on the total weight of the aqueoussolution, of phosphoric acid. Solution B was prepared by blending coppersulphate pentahydrate, CuSO₄.5H₂O into a solution of phosphoric acidsuch that the final solution contained 25 wt.-%, based on the totalweight of the aqueous solution, of phosphoric acid and 4.2 wt.-%, basedon the total weight of the aqueous solution, of copper ion.

Whilst mixing the slurry, 534 g of solution A was added to the 10 wt.-%calcium carbonate suspension over a period of 6 minutes. Directly aftersolution A finished adding, 640 g of solution B was added to thesuspension over a period of 8 minutes. Throughout the whole experimentthe temperature of the suspension was maintained at 70° C. Finally,after the addition of solution B, the suspension was stirred foradditional 5 minutes before removing it from the vessel and drying. Theobtained surface-reacted calcium carbonate had the following properties:d₅₀=5.0 μm, d₉₈=8.8 μm, SSA=34.2 m²g⁻¹. The intra-particle intrudedspecific pore volume was 0.48 cm³/g (for the pore diameter range of0.004 to 0.20 μm).

Surface-Reacted Calcium Carbonate SRCC 5 (Inventive)

SRCC 5 was obtained by preparing 10 litres of an aqueous suspension ofground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground marble calcium carbonate from Hustadmarmor Norwayhaving a mass based particle size distribution of 90% less than 2 μm, asdetermined by sedimentation, such that a solids content of 10 wt.-%,based on the total weight of the aqueous suspension, is obtained.

In addition, two solutions were prepared. Solution A was prepared suchthat it contained 30 wt.-%, based on the total weight of the aqueoussolution, of phosphoric acid. Solution B was prepared by blending coppersulphate pentahydrate, CuSO₄.5H₂O into a solution of phosphoric acidsuch that the final solution contained 25 wt.-%, based on the totalweight of the aqueous solution, of phosphoric acid and 4.2 wt.-%, basedon the total weight of the aqueous solution, of copper ion.

Whilst mixing the slurry, 534 g of solution A was added to the 10 wt.-%calcium carbonate suspension over a period of 5 minutes. Directly aftersolution A finished adding, 640 g of solution B was added to thesuspension over a period of 15 minutes. Throughout the whole experimentthe temperature of the suspension was maintained at 70° C. Finally,after the addition of solution B, the suspension was stirred foradditional 5 minutes before removing it from the vessel and drying. Theobtained surface-reacted calcium carbonate had the following properties:d₅₀=5.2 μm, d₉₈=8.9 μm, SSA=34.8 m²g⁻¹. The intra-particle intrudedspecific pore volume was 0.49 cm³/g (for the pore diameter range of0.004 to 0.22 μm).

Surface-Reacted Calcium Carbonate SRCC 6 (Inventive)

SRCC 6 was obtained by preparing 10 litres of an aqueous suspension ofground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground marble calcium carbonate from Hustadmarmor Norwayhaving a mass based particle size distribution of 90% less than 2 μm, asdetermined by sedimentation, such that a solids content of 10 wt.-%,based on the total weight of the aqueous suspension, is obtained.

In addition, two solutions were prepared. Solution A was prepared suchthat it contained 30 wt.-%, based on the total weight of the aqueoussolution, of phosphoric acid. Solution B was prepared by blending zincchloride anhydrous, ZnCl₂, into a solution of phosphoric acid such thatthe final solution contained 27.3 wt.-%, based on the total weight ofthe aqueous solution, of phosphoric acid and 4.4 wt.-%, based on thetotal weight of the aqueous solution, of zinc ion.

Whilst mixing the slurry, 534 g of solution A was added to the 10 wt.-%calcium carbonate suspension over a period of 5 minutes. Directly aftersolution A finished adding, 587 g of solution B was added to thesuspension over a period of 6 minutes. Throughout the whole experimentthe temperature of the suspension was maintained at 70° C. Finally,after the addition of solution B, the suspension was stirred foradditional 5 minutes before removing it from the vessel and drying. Theobtained surface-reacted calcium carbonate had the following properties:d₅₀=5.5 μm, d₉₈=10.0 μm, SSA=43.2 m²g⁻¹) The intra-particle intrudedspecific pore volume is 0.756 cm³/g (for the pore diameter range of0.004 to 0.31 μm).

Surface-Reacted Calcium Carbonate SRCC 7 (Inventive)

SRCC 7 was obtained by preparing 10 litres of an aqueous suspension ofground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground marble calcium carbonate from Hustadmarmor Norwayhaving a mass based particle size distribution of 90% less than 2 μm, asdetermined by sedimentation, such that a solids content of 10 wt.-%,based on the total weight of the aqueous suspension, is obtained.

In addition, two solutions were prepared. Solution A was prepared suchthat it contained 30 wt.-%, based on the total weight of the aqueoussolution, of phosphoric acid. Solution B was prepared by blending zincchloride anhydrous, ZnCl₂, into a solution of phosphoric acid such thatthe final solution contained 25 wt.-%, based on the total weight of theaqueous solution, of phosphoric acid and 8.0 wt.-%, based on the totalweight of the aqueous solution, of zinc ion.

Whilst mixing the slurry, 534 g of solution A was added to the 10 wt.-%calcium carbonate suspension over a period of 5 minutes. Directly aftersolution A finished adding, 640 g of solution B was added to thesuspension over a period of 7 minutes. Throughout the whole experimentthe temperature of the suspension was maintained at 70° C. Finally,after the addition of solution B, the suspension was stirred foradditional 5 minutes before removing it from the vessel and drying. Theobtained surface-reacted calcium carbonate had the following properties:d₅₀=8.3 μm, d₉₈=19.3 μm, SSA=30.1 m²g⁻¹) The intra-particle intrudedspecific pore volume is 0.740 cm³/g (for the pore diameter range of0.004 to 0.43 μm).

Surface-Reacted Calcium Carbonate SRCC 8 (Inventive)

SRCC 8 was obtained by preparing 10 litres of an aqueous suspension ofground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground limestone calcium carbonate from Orgon, Francehaving a mass based median particle size of 3 μm, as determined bysedimentation, such that a solids content of 10 wt.-%, based on thetotal weight of the aqueous suspension, is obtained.

In addition, two solutions were prepared. Solution A was prepared suchthat it contained 30 wt.-%, based on the total weight of the aqueoussolution, of phosphoric acid. Solution B was prepared by blending zincchloride anhydrous, ZnCl₂, into a solution of phosphoric acid such thatthe final solution contained 27.3 wt.-%, based on the total weight ofthe aqueous solution, of phosphoric acid and 4.4 wt.-%, based on thetotal weight of the aqueous solution, of zinc ion.

Whilst mixing the slurry, 534 g of solution A was added to the 10 wt.-%calcium carbonate suspension over a period of 5 minutes. Directly aftersolution A finished adding, 587 g of solution B was added to thesuspension over a period of 6 minutes. Throughout the whole experimentthe temperature of the suspension was maintained at 70° C. Finally,after the addition of solution B, the suspension was stirred foradditional 5 minutes before removing it from the vessel and drying. Theobtained surface-reacted calcium carbonate had the following properties:d₅₀=11.0 μm, d₉₈=25.3 μm, SSA=27.6 m²g⁻¹. The intra-particle intrudedspecific pore volume is 0.717 cm³/g (for the pore diameter range of0.004 to 0.75 μm).

Powder 9 (Inventive) a Mix of SRCC 3 and SRCC 11

400 g of a 22 wt.-% solid content filter cake from sample SRCC 3 weredispersed in 1 litres deionized water, agitated with a mechanicalstirrer for approx. 20 minutes (300-350 rpm) and then filtered on aBuchner funnel. This procedure was repeated a second time, and, afterthe second washing step, the filter cake was dried in an oven (110° C.)and deagglomerated.

20 g of the above powder were then mixed with 180 g of SRCC 11.

Powder 10 (Inventive) —a Mix of SRCC 5 and SRCC 11

400 g of a 24.5 wt.-% solid content filter cake from sample SRCC 5 weredispersed in 1 L deionized water, agitated with a mechanical stirrer forca. 20 minutes (300-350 rpm) and then filtered on a Buchner funnel. Thisprocedure was repeated a second time, and, after the second washingstep, the filter cake was dried in an oven (110° C.) and deagglomerated.

20 g of the above powder were then mixed with 180 g of SRCC 11.

Surface-Reacted Calcium Carbonate SRCC 11 (Comparative)

SRCC 11 is a surface-reacted calcium carbonate (d₅₀=2.6 μm, BET=34.7m²/g, and an intra-particle intruded specific pore volume of 0.305 cm³/g(for the pore diameter range of 0.004 to 0.19 μm), without furthertreatment.

Surface-Reacted Calcium Carbonate SRCC 12 (Inventive)

SRCC 12 was obtained by preparing 0.5 a litre of an aqueous suspensionof ground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground marble calcium carbonate from Hustadmarmor Norwayhaving a mass based particle size distribution of 90% less than 2 μm, asdetermined by sedimentation, such that a solids content of 10 wt.-%,based on the total weight of the aqueous suspension, is obtained.

In addition, a solution was prepared containing 29.1% by mass phosphoricacid and 3.1% by mass of chloroplatinic acid hexahydrate, H₂PtCl₆.6H₂O.

Whilst mixing the slurry, 91.8 g of the phosphoric acid/chloroplatinicacid hexahydrate solution was added to said suspension over a period of10 minutes at a temperature of 70° C. Finally, after the addition of thephosphoric acid, the slurry was stirred for additional 5 minutes, beforeremoving it from the vessel. Then, the slurry was dried by use of arotary evaporator. The obtained surface-reacted calcium carbonate hadthe following properties: d₅₀=8.8 μm, d₉₈=19.9 μm, SSA=53.9 m²g⁻¹. Theintra-particle intruded specific pore volume is 1.415 cm³/g (for thepore diameter range of 0.004 to 0.67 μm).

Surface-Reacted Calcium Carbonate SRCC 13 (Inventive)

SRCC 13 was obtained by preparing 0.5 a litre of an aqueous suspensionof ground calcium carbonate in a mixing vessel by adjusting the solidscontent of a ground marble calcium carbonate from Hustadmarmor Norwayhaving a mass based particle size distribution of 90% less than 2 μm, asdetermined by sedimentation, such that a solids content of 10 wt.-%,based on the total weight of the aqueous suspension, is obtained.

In addition, two solutions were prepared. Solution A was prepared suchthat it contained 30 wt.-%, based on the total weight of the aqueoussolution, of phosphoric acid. Solution B was prepared by blendingchloroplatinic acid hexahydrate, H₂PtCl₆.6H₂O into a solution ofphosphoric acid such that the final solution contained 28.2 wt.-%, basedon the total weight of the aqueous solution, of phosphoric acid and 2.3wt.-%, based on the total weight of the aqueous solution, of platinumion.

Whilst mixing the slurry, 44.5 g of solution A was added to the 10 wt.-%calcium carbonate suspension over a period of 5 minutes. Directly aftersolution A finished adding, 47.3 g of solution B was added to thesuspension over a period of 5 minutes. Throughout the whole experimentthe temperature of the suspension was maintained at 70° C. Finally,after the addition of solution B, the suspension was stirred foradditional 5 minutes before removing it from the vessel and drying. Theobtained surface-reacted calcium carbonate had the following properties:d₅₀=8.5 μm, d₉₈=18.1 μm, and SSA=57.8 m²g⁻¹. The intra-particle intrudedspecific pore volume was 1.417 cm³/g (for the pore diameter range of0.004 to 0.67 μm).

3. Analysis

TABLE 1 Quantitative Rietveld analyses (XRD) SRCC 11 SRCC 3 SRCC 4 SRCC5 (compar- (inven- (inven- (inven- Mineral Formula ative) tive) tive)tive) Calcite CaCO₃ 73.7 51.2 58.5 58.8 Hydroxylapatite Ca₅(OH)(PO₄)₃26.3 46.1 25.4 25.6 Monetite CaHPO₄ — 2.7 15.8 15.4 BrochantiteCu₄SO₄(OH)₆ — — 0.3 0.2 Total 100 100 100 100 Data were normalized to100% crystalline material.

ICP-OES

TABLE 2 Composition of powder samples after filtration. SRCC 3 SRCC 5 Cu(ICP-OES, %) 0.56 2.16

TABLE 3 Composition of filtered washing water from Powder 5. 1 L washingCalcium 336 ± 5 ppm; ROR^(a)): 95.0% Copper <0.1 ppm ^(a))ROR means rateof recovery of the measurement.

The XRD measurements show that a new crystalline calcium phase(monetite) has been formed in the inventive surface-reacted calciumcarbonate. Furthermore, the inventive samples SRCC4 and SRCC5 show thepresence of a copper mineral phase, namely, brochantite. The XRDmeasurements of SRCC3 did not reveal a significant copper phase.However, it could be confirmed by ICP-OES that SRCC3 contains copper.

For the analysis according to Table 3, 400 g of SRCC 5 filter cake(corresponding to 98 g solid) are dispersed with 1 litre deionised waterand agitated (mechanical agitation, ca 300 rpm) for 30 minutes. Thesuspension is filtered, and the filtered solution is analysed todetermine the amount of copper in 1 litre water. It can be gathered fromTable 3 that only a very low amount of copper was leached into thewater.

4. Slurries of Surface-Reacted Calcium Carbonate Fillers and PaperCoatings

Examples 1 to 5 (E1 to E5) and Comparative Example 1 (CE1)

Slurries were prepared on a Pendraulik stirrer, by stirring mixtures ofthe compositions indicated in Table 4 below for 10 minutes at roomtemperature with 930 rpm.

TABLE 4 Composition of produced filler slurries. SRCC Water DA SolidBrookfield [parts by [parts by [parts by content viscosity ConductivityExample SRCC weight] weight] weight] [wt.-%] [m · Pas] pH [mS/cm] CE1SRCC 11 100 100 0.7 46.7 348 9.2 1.7 E1 SRCC 1  100^(a) 465 0.7 17.7 9927.5 1.2 E2 SRCC 3  100^(b) 405 0.7 19.5 1188 6.9 1.8 E3 SRCC 5  100^(c)435 0.7 18.7 1098 6.6 2.0 E4 Powder 9 - mix of 100 125 0.7 41.4 108.48.9 1.8 SRCC 3 and SRCC 11 washed (90:10 mixture) E5 Powder 10 - mix 100125 0.7 41.6 138 8.7 1.9 of SRCC 5 and SRCC 11 washed (90:10 mixture)^(a)a 20.3 wt.-% filter cake from SRCC 1 was used. ^(b)a 24.5 wt.-%filter cake from SRCC 3 was used. ^(c)a 24.5 wt.-% filter cake from SRCC5 was used. DA = dispersing agent (100% sodium-neutralised polyacrylate,M_(w) = 3 500 g/mol, pH = 8).

Coating colours containing 100 parts of the respective SRCC (w/w) and 6parts (dry/dry) of Styronal D628 (BASF, Germany) were then prepared withslurries according to Examples 1 to 5 and Comparative Examples 1 andcoated on superYUPO® foils from Fischer Papier AG, Switzerland(thickness 80 μm, size: 18×26 cm², 62 g/m², polypropylene). Thecomposition of the coating colours and coating weights are summarized inTable 5 below.

TABLE 5 Coating colour preparation and coating weight. Coating colourcomposition SRCC Styronal [parts D628 Solid Coating by [parts, contentweight Example Slurry weight] dry/dry] [wt.-%] [g/m²] CE2 CE1 (SRCC 11)100 6 40 12.4 E6 E1 (SRCC 1) 100 6 18 4.4 E7 E2 (SRCC 3) 100 6 18 4.6 E8E3 (SRCC 5) 100 6 18 8.1 E9 E4 (Powder 9 − mix of 100 6 40 14.5 SRCC 3and SRCC 11 washed (90:10 mixture)) E10 E5 (Powder 10 − mix of 100 6 4013 SRCC 5 and SRCC 11 washed (90:10 mixture))

Example 11 Antimicrobial Surface Activity of Paper Coatings

The antimicrobial activity of selected paper samples comprising acoating layer containing the surface-reacted calcium carbonate of thepresent invention as filler, which were prepared according to Examples 6to 10 (E6 to E10) and Comparative

Example 2 (CE2) was tested as described in the measurement methodsection “Antimicrobial surface activity test” above.

Tables 6 shows the cfu counts per test item and the calculatedantimicrobial activity against S. aureus of the coated paper samples E6to E10 as well as of comparative sample CE2. The term LOD in Table 6refers to the limit of detection.

TABLE 6 Antimicrobial activity against S. aureus of surface coated papersamples. Antimicrobial cfu/test item activity Test item I II III AverageR LOD untreated paper from 2.9E+05 2.6E+05 2.5E+05 2.7E+05 N/A N/A CE2(SRCC 11) (before incubation) untreated paper from 3.5E+03 1.6E+041.6E+04 1.2E+04 0.00 3.07 CE2 (SRCC 11) Paper from E6 (SRCC 1) 1.0E+011.0E+01 1.0E+01 1.0E+01 3.07 3.07 Paper from E7 (SRCC 3) 1.0E+01 1.0E+011.0E+01 1.0E+01 3.07 3.07 Paper from E8 (SRCC 5) 1.0E+01 1.0E+01 1.0E+011.0E+01 3.07 3.07 Paper from E9 (Powder 9 - 1.0E+01 1.0E+01 1.0E+011.0E+01 3.07 3.07 mix of SRCC 3 and SRCC 11 washed (90:10 mixture))Paper from E10 (Powder 1.0E+01 1.0E+01 1.0E+01 1.0E+01 3.07 3.07 10 -mix of SRCC 5 and SRCC 11 washed (90:10 mixture)) N/A: Not applicable.

As can be gathered from the results compiled in Table 6 above, all papersamples with a coating layer comprising the inventive surface-reactedcalcium carbonate show good antimicrobial activity.

1. A process of producing a surface-reacted calcium carbonate, theprocess comprising the steps of: a) providing a calciumcarbonate-comprising material, b) providing at least one H₃O⁺ ion donor,c) providing at least one water-soluble metal cation source, and d)treating the calcium carbonate-comprising material of step a) with theat least one H₃O⁺ ion donor of step b) and carbon dioxide in an aqueousmedium to form an aqueous suspension of surface-reacted calciumcarbonate, wherein the carbon dioxide is formed in-situ by the H₃O⁺ iondonor treatment and/or is supplied from an external source, and whereinthe at least one water-soluble metal cation source of step c) is addedduring step d).
 2. The process of claim 1, wherein the calciumcarbonate-comprising material is a natural ground calcium carbonateand/or a precipitated calcium carbonate.
 3. The process of claim 1,wherein the calcium carbonate-comprising material is in the form ofparticles having a weight median particle size d₅₀(wt) from 0.05 μm to10 μm.
 4. The process of claim 1, wherein the at least one H₃O⁺ iondonor is selected from the group consisting of hydrochloric acid,sulphuric acid, sulphurous acid, phosphoric acid, citric acid, oxalicacid, an acidic salt, acetic acid, formic acid, and mixtures thereof. 5.The process of claim 1, wherein the molar ratio of the at least one H₃O⁺ion donor to the calcium carbonate-comprising material is from 0.01 to4.
 6. The process of claim 1, wherein the at least one water-solublemetal cation source is selected from the group consisting of awater-soluble metal salt, a water-soluble transition metal complex, awater-soluble metal hydroxide, a water-soluble metal oxide, and mixturesthereof.
 7. The process of claim 1, wherein the at least onewater-soluble metal cation source is provided in an amount from 0.01wt.-% to 60 wt.-%, based on the total weight of the calciumcarbonate-comprising material.
 8. The process of claim 1, wherein instep d) the calcium carbonate-comprising material is treated with asolution comprising the at least one H₃O⁺ ion donor of step b) and theat least one water-soluble metal cation source of step c).
 9. Theprocess of claim 1, wherein in step d) the calcium carbonate-comprisingmaterial is treated with a first solution comprising a first part of theat least one H₃O⁺ ion donor of step b), and subsequently, with a secondsolution comprising the remaining part of the at least one H₃O⁺ iondonor of step b) and the at least one water-soluble metal cation sourceof step c).
 10. The process of claim 1, wherein step d) is carried outat a temperature from 20° C. to 90° C.
 11. The process of claim 1,wherein the process further comprises a step e) of separating thesurface-reacted calcium carbonate from the aqueous suspension obtainedin step d).
 12. The process of claim 1, wherein the process furthercomprises a step f) of drying the surface-reacted calcium carbonateafter step d) or after step e), if present, at a temperature in therange from 60° C. to 600° C.
 13. The process of claim 1, wherein thecalcium carbonate-comprising material is a natural ground calciumcarbonate, the at least one H₃O⁺ ion donor is phosphoric acid, the atleast one water-soluble metal cation source is selected from the groupconsisting of copper nitrate, copper sulphate, copper acetate, copperchloride, copper bromide, copper iodide, zinc nitrate, zinc sulphate,zinc acetate, zinc chloride, zinc bromide, zinc iodide, hydratesthereof, and mixtures thereof, and in step d) the calciumcarbonate-comprising material is treated with a solution comprising theat least one H₃O⁺ ion donor of step b) and the at least onewater-soluble metal cation source of step c).
 14. A surface-reactedcalcium carbonate obtained by the process according to claim
 1. 15. Thesurface-reacted calcium carbonate of claim 14, wherein thesurface-reacted calcium carbonate has a specific surface area of from 15m²/g to 200 m²/g measured using nitrogen and the BET method.
 16. Thesurface-reacted calcium carbonate of claim 14, wherein thesurface-reacted calcium carbonate has a volume determined medianparticle size d₅₀(vol) from 1 μm to 75 μm and/or a volume determined topcut particle size d₉₈(vol) from 2 μm to 150 μm.
 17. The surface-reactedcalcium carbonate of claim 14, wherein the surface-reacted calciumcarbonate has an intra-particle intruded specific pore volume in therange from 0.1 cm³/g to 2.3 cm³/g calculated from mercury porosimetrymeasurement.
 18. The surface-reacted calcium carbonate of claim 14,wherein the surface-reacted calcium carbonate has an intra-particle poresize in a range of from 0.004 μm to 1.6 μm determined from mercuryporosity measurement.
 19. A composition comprising a surface-reactedcalcium carbonate according to claim 14, the composition furthercomprising an additional surface-reacted calcium carbonate, wherein theadditional surface-reacted calcium carbonate is a reaction product ofnatural ground calcium carbonate or precipitated calcium carbonate withcarbon dioxide and at least one H₃O⁺ ion donor, wherein the carbondioxide is formed in-situ by the H₃O⁺ ion donor treatment and/or issupplied from an external source.
 20. A method of preserving,controlling an odor, and/or enhancing and/or mediating antimicrobialactivity of a substrate, the method comprising administering asurface-reacted calcium carbonate according to claim 14 in an amountsufficient to act as a preservative, to control the odor and/or enhanceand/or mediate the antimicrobial activity of the substrate.
 21. A methodof providing micronutrient delivery and/or plant protection, the methodcomprising administering an effective amount of a the surface-reactedcalcium carbonate according to claim 14 as a metal cation releaser todeliver the micronutrient and/or provide the plant protection.
 22. Amethod of enhancing electrical conductivity of a substrate, the methodcomprising administering an effective amount of the surface-reactedcalcium carbonate according to claim 14 to enhance the electricalconductivity of the substrate.
 23. A polymer application, paper coatingapplication, paper making, paint, coating, sealant, printing ink,adhesive, food, feed, pharmaceutical, concrete, cement, cosmetic, watertreatment, engineered wood application, plasterboard application,packaging application and/or agricultural application comprising aneffective amount of the surface-reacted calcium carbonate according toclaim
 14. 24. An article comprising a surface-reacted calcium carbonateaccording to claim 14, wherein the article is selected from the groupconsisting of paper products, engineered wood products, plasterboardproducts, polymer products, hygiene products, medical products,healthcare products, filter products, woven materials, nonwovenmaterials, geotextile products, agriculture products, horticultureproducts, clothing, footwear products, baggage products, householdproducts, industrial products, packaging products, building products,and construction products.
 25. The process of claim 2, wherein thenatural ground calcium carbonate is selected from the group consistingof marble, chalk, dolomite, limestone, and mixtures thereof, and/or theprecipitated calcium carbonate is selected from the group consisting ofprecipitated calcium carbonates having an aragonitic, vateritic orcalcitic crystal form, and mixtures thereof.
 26. The process of claim 3,wherein the weight median particle size d₅₀(wt) is in a range selectedfrom the group consisting of from 0.2 μm to 5.0 μm, from 0.4 μm to 3.0μm and from 0.6 μm to 1.2 μm, and/or the weight top cut particle sized₉₈(wt) is in a range selected from the group consisting of from 1 μm to40 μm, from 2 μm to 25 μm, and from and 3 μm to 15 μm.
 27. The processof claim 5, wherein the molar ratio is from 0.02 to 2, 0.05 to 1, orfrom 0.1 to 0.58.
 28. The process of claim 7, wherein the amount of theat least one water-soluble metal cation source is in a range selectedfrom the group consisting of from 0.05 wt.-% to 50 wt.-%, from 0.1 wt.-%to 25 wt.-% and from 0.5 wt.-% to 10 wt.-%.
 29. The process of claim 12,wherein the drying is conducted until the moisture content of thesurface-reacted calcium carbonate is from 0.01 wt.-% to 5 wt.-% based onthe total weight of the dried surface-reacted calcium carbonate.
 30. Theprocess of claim 15, wherein the specific surface area is in a rangeselected from the group consisting of from 20 m²/g to 180 m²/g, from 25m²/g to 160 m²/g, from 27 m²/g to 150 m²/g and from 30 m²/g to 140 m²/g.31. The process of claim 16, wherein the volume determined medianparticle size d₅₀(vol) is in a range of from 2 μm to 50 μm, from 3 μm to40 μm, from 4 μm to 30 μm and from 5 μm to 15 μm and/or the volumedetermined top cut particle size do(vol) is in a range selected from thegroup consisting of from 4 μm to 100 μm, from 6 μm to 80 μm, from 8 μmto 60 μm and from 10 μm to 30 μm.
 32. The process of claim 17, whereinthe intra-particle intruded specific pore volume is in a range of from0.2 cm²/g to 2.0 cm³/g, from 0.4 cm³/g to 1.8 cm³/g or from 0.6 cm ³/gto 1.6 cm³/g.
 33. The process of claim 18, wherein the intra-particlepore size is in a range of from 0.005 μm to 1.3 μm, from 0.006 μm to1.15 μm or from 0.007 μm to 1.0 μm.